A258184 Numbers which divide the concatenation of the next two primes.

1, 3, 7, 61, 167, 801, 1143, 2001, 6001, 8001, 125001, 25000001, 181818181819, 2500000000001, 16666666666667, 45000000000001, 640000000000001, 1142857142857143, 4000000000000001, 37500000000000001, 153846153846153847, 937500000000000001, 2881355932203389831

Offset

1,2

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..40 (terms < 10^36)

Carlos Rivera, Puzzle 786

Example

The number 7 is in the sequence since the next two primes are 11 and 13 and 1113 is divisible by 7.

Mathematica

Select[Range[10^5], Divisible[ FromDigits[ Join@@ IntegerDigits@ NextPrime[#, {1, 2}]], #]&]

Crossrefs

Cf. A258182, A258183.

Sequence in context: A183174 A329966 A255669 * A362347 A077703 A134705

Adjacent sequences: A258181 A258182 A258183 * A258185 A258186 A258187

Keyword

nonn,base

Author

Giovanni Resta, May 23 2015

Status

approved