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Search: id:A073669
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| A073669 |
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a(1) = 1, a(n) = the smallest composite multiple of n such that every partial sum is prime. |
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+0
2
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| 1, 4, 6, 8, 10, 12, 42, 24, 72, 20, 132, 36, 52, 14, 30, 16, 68, 54, 76, 80, 126, 88, 92, 24, 100, 26, 108, 112, 116, 30, 310, 128, 66, 204, 70, 36, 74, 76, 78, 120, 902, 84, 430, 44, 360, 460, 188, 240, 294, 100, 204, 104, 106, 54, 110, 280, 342, 116, 708, 60, 244, 62
(list; graph; listen)
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OFFSET
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1,2
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MAPLE
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a[1] := 1:su := 1:for n from 2 to 112 do i := 1: if(isprime(n)) then i := i+1:fi:while(not isprime(i*n+su)) do i := i+1:od:a[n] := i*n:su := su+a[n]:od:seq(a[j], j=1..112);
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MATHEMATICA
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a[1]=s[1]=1; s[n_] := s[n]=s[n-1]+a[n]; a[n_] := a[n]=For[i=1, True, i++, If[ !PrimeQ[i*n]&&PrimeQ[s[n-1]+i*n], Return[i*n]]]
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CROSSREFS
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Sequence in context: A131694 A053012 A096160 this_sequence A073670 A090169 A087684
Adjacent sequences: A073666 A073667 A073668 this_sequence A073670 A073671 A073672
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 11 2002
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EXTENSIONS
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Corrected and extended by Sascha Kurz (sascha.kurz(AT)uni-bayreuth.de), Jan 30 2003
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