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Search: id:A089823
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| A089823 |
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Primes p such that the next prime after p can be obtained from p by adding the product of the digits of p. |
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+0
8
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| 23, 61, 1123, 1231, 1321, 2111, 2131, 11261, 11621, 12113, 13121, 15121, 19121, 21911, 22511, 27211, 61211, 116113, 131231, 312161, 611113, 1111211, 1111213, 1111361, 1112611, 1123151, 1411411, 1612111, 2111411, 2121131, 3112111
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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I call these primes (multiplicative) "pointer primes", in the sense that such primes p "point" to the next prime after p when the product of the digits of p is added to p. 23 is the only pointer prime < 10^7 which does not contain the digit "1". Are there other pointer primes not containing the digit "1"?
See Prime Puzzle 251 link for several arguments that 23 is the only pointer prime not containing digit "1".
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LINKS
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Carlos Rivera's Prime Puzzles and Problems Connection, Puzzle 251, Pointer primes
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EXAMPLE
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23 + product of digits of 23 = 29, which is the next prime after 23. Hence 23 belongs to the sequence.
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MATHEMATICA
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r = {}; Do[p = Prime[i]; q = Prime[i + 1]; If[p + Apply[Times, IntegerDigits[p]] == q, r = Append[r, p]], {i, 1, 10^6}]; r
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CROSSREFS
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Cf. A091628, A091629, A091630, A091631, A091632.
Sequence in context: A069798 A067194 A107692 this_sequence A001346 A051875 A125872
Adjacent sequences: A089820 A089821 A089822 this_sequence A089824 A089825 A089826
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KEYWORD
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base,nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 09 2004
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