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Search: id:A101988
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| A101988 |
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Number of primes (with repetition) that can be formed from digits of the n-th prime. |
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+0
2
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| 1, 1, 1, 1, 1, 3, 3, 1, 3, 2, 3, 4, 1, 2, 2, 3, 2, 1, 2, 3, 4, 3, 2, 1, 3, 3, 7, 8, 3, 9, 6, 9, 11, 6, 6, 3, 7, 7, 8, 11, 10, 3, 5, 6, 10, 5, 3, 6, 4, 5, 6, 6, 4, 4, 4, 4, 3, 6, 5, 3, 6, 6, 9, 9, 8, 11, 8, 10, 8, 4, 6, 7, 7, 10, 10, 5, 6, 10, 3, 1, 6, 4, 6, 5, 4, 4, 1, 5, 4, 4, 5, 6, 3, 6, 1, 7, 5, 4, 6, 3, 5, 4
(list; graph; listen)
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OFFSET
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1,6
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COMMENT
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Here we put all the digits of prime(n) into a bag and ask how many not necessarily distinct primes can be formed using some or all of these digits.
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EXAMPLE
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a(35)=6 because from the digits of p(35)=149, six numbers can be formed, 19, 41, 149, 419, 491 & 941, which are primes.
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MATHEMATICA
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(* first do *) Needs["DiscreteMath`Combinatorica`"] (* then *) f[n_] := Length[ Select[ FromDigits /@ Flatten[ Permutations /@ Subsets[ IntegerDigits[ Prime[n]]], 1], PrimeQ[ # ] &] ]; Table[ f[n], {n, 102}] (from Robert G. Wilson v Feb 10 2005)
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CROSSREFS
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Cf. A039992, A045719.
Sequence in context: A030778 A068119 A039992 this_sequence A088420 A103585 A154595
Adjacent sequences: A101985 A101986 A101987 this_sequence A101989 A101990 A101991
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KEYWORD
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base,easy,nonn
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AUTHOR
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Zak Seidov (seidovzf(AT)yahoo.com), Jan 29 2005
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EXTENSIONS
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Corrected and extended by Robert G. Wilson v (rgwv(AT)rgwv.com), Feb 10 2005. Definition clarified by Ray Chandler, Mar 01, 2005.
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