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A258183
Numbers which divide the concatenation of the two surrounding primes.
3
7, 9, 49, 111, 1090909, 28571427, 111111111, 3333333327, 25641025641, 10576923076923, 59090909090909, 2631578947368421, 4827586206896549, 8947368421052631, 18644067796610169, 111111111111111111, 812499999999999999, 1889250814332247557, 9189189189189189189
OFFSET
1,1
COMMENTS
The terms greater than 10^18 are obtained assuming that nextprime(n) < n + (log n)^2, which is known to hold at least for 4 < n < 10^18.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..42 (terms < 10^36)
Carlos Rivera, Puzzle 786
EXAMPLE
The number 9 is in the sequence because the surrounding primes are 7 and 11 and 711 is divisible by 9.
MATHEMATICA
Select[Range[3, 10^4], Divisible[ FromDigits[ Join@@ IntegerDigits@ NextPrime[#, {-1, 1}]], #]&]
CROSSREFS
Sequence in context: A189053 A067649 A025631 * A038275 A261669 A299913
KEYWORD
nonn,base
AUTHOR
Giovanni Resta, May 23 2015
STATUS
approved