A049653 - OEIS

A049653

a(n) = 2*n - prevprime(2*n).

1, 1, 1, 3, 1, 1, 3, 1, 1, 3, 1, 3, 5, 1, 1, 3, 5, 1, 3, 1, 1, 3, 1, 3, 5, 1, 3, 5, 1, 1, 3, 5, 1, 3, 1, 1, 3, 5, 1, 3, 1, 3, 5, 1, 3, 5, 7, 1, 3, 1, 1, 3, 1, 1, 3, 1, 3, 5, 7, 9, 11, 13, 1, 3, 1, 3, 5, 1, 1, 3, 5, 7, 9, 1, 1, 3, 5, 1, 3, 5, 1, 3, 1, 3, 5, 1, 3, 5, 1, 1, 3, 5, 7

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OFFSET

2,4

LINKS

G. C. Greubel, Table of n, a(n) for n = 2..5000

FORMULA

a(n) = A049711(2*n). - R. J. Mathar, Oct 26 2015

MATHEMATICA

Table[2*n - NextPrime[2*n, -1], {n, 2, 50}] (* G. C. Greubel, Dec 05 2017 *)

PROG

(Magma) [2*n - NthPrime(#PrimesUpTo(2*n)): n in [2..50]]; // G. C. Greubel, Dec 05 2017

(PARI) for(n=2, 50, print1(2*n - precprime(2*n), ", ")) \\ G. C. Greubel, Dec 05 2017