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Search: id:A125088
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| A125088 |
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a(1)=1. a(n) = sum of the earlier terms equal to any exponent in the prime-factorization of n. |
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+0
2
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| 1, 1, 2, 2, 2, 2, 2, 0, 10, 2, 2, 16, 2, 2, 2, 0, 2, 24, 2, 26, 2, 2, 2, 2, 32, 2, 0, 36, 2, 2, 2, 0, 2, 2, 2, 46, 2, 2, 2, 2, 2, 2, 2, 62, 62, 2, 2, 2, 66, 68, 2, 70, 2, 2, 2, 2, 2, 2, 2, 84, 2, 2, 88, 0, 2, 2, 2, 94, 2, 2, 2, 98, 2, 2, 104, 104, 2, 2, 2, 2, 0, 2, 2, 116, 2, 2, 2, 2, 2, 126, 2, 128
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Only a(1) & a(2) are odd. a(n)=0 for n>1 in A036966. - Robert G. Wilson v Nov 22 2006.
Only possible values: ....... 0, 1, 2, 10, 16, 24, 26, 32, 36, 46, 62, 66, 68, 70, 84, 88, 94, 98, 104, ..., . - Robert G. Wilson v Nov 22 2006.
Position of first occurrence: 8, 1, 3, 9, 12, 18, 20, 25, 28, 36, 44, 49, 50, 52, 60, 63, 68, 72, 75, ..., . - Robert G. Wilson v Nov 22 2006.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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12 has a prime factorization of 2^2 *3^1. So a(12) is the sum of the terms among the first 11 terms of the sequence which equal 1 or 2. There are seven 2's and two 1's among the first 11 terms; so a(12) = 1+1+2+2+2+2+2+2+2 = 16.
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MATHEMATICA
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f[l_List] := Append[l, Plus @@ Select[l, MemberQ[Last /@ FactorInteger[Length[l] + 1], # ] &]]; Nest[f, {1}, 91] (*Chandler*)
a[1] = 1; a[n_] := a[n] = Plus @@ Flatten[ Cases[ Array[a, n - 1], # ] & /@ Union@ Last@ Transpose@ FactorInteger@n]; Array[a, 92] (* Robert G. Wilson v *)
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CROSSREFS
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Cf. A125087.
Sequence in context: A137934 A133738 A111409 this_sequence A027360 A037806 A038082
Adjacent sequences: A125085 A125086 A125087 this_sequence A125089 A125090 A125091
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Nov 19 2006
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Nov 21 2006
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