A280023 Least k such that A002375(k) = A002375(k+n), or 0 if no such k exists.

1, 4, 3, 5, 5, 8, 7, 8, 5, 9, 5, 7, 13, 5, 11, 12, 11, 13, 12, 11, 23, 18, 17, 10, 9, 8, 7, 18, 5, 32, 36, 29, 31, 15, 27, 13, 12, 11, 35, 21, 27, 22, 18, 17, 37, 54, 27, 56, 15, 24, 13, 12, 11, 60, 21, 30, 37, 18, 17, 56, 30, 32, 105, 39, 39, 58, 27, 48, 55, 24, 53, 85, 33, 39, 71, 30, 39, 130, 42, 45, 100, 45, 56, 85, 66, 42, 105, 36, 45, 109, 33, 54, 70, 30, 51, 98, 39, 65, 67, 39, 57, 97, 51

Offset: 1

Author

Altug Alkan, Feb 22 2017

Keywords

• nonn

Examples

			a(2) = 4 because smallest k such that A002375(k) = A002375(k+2) is 4; A002375(4) = A002375(6) = 1.
		

Links

• Altug Alkan, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002375.

Programs

PARI

a002375(n) = sum(i=2, primepi(n), isprime(2*n - prime(i)));
a(n) = my(k=1); while (a002375(n+k) != a002375(k), k++); k;