A184728 - OEIS

A184728

a(n) = largest k such that A001358(n+1) = A001358(n) + (A001358(n) mod k), or 0 if no such k exists.

0, 0, 8, 6, 13, 9, 20, 19, 24, 19, 32, 33, 32, 37, 32, 43, 47, 47, 53, 56, 54, 59, 61, 64, 71, 72, 79, 84, 85, 83, 89, 92, 93, 84, 101, 107, 112, 117, 117, 120, 121, 117, 125, 132, 127, 140, 141, 141, 144, 137, 152, 157, 157

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OFFSET

1,3

COMMENTS

a(n) = A001358(n) - A065516(n) if A001358(n) - A065516(n) > A065516(n), 0 otherwise.

A001358(n): semiprimes; A065516(n): first difference of semiprimes.

LINKS

Rémi Eismann, Table of n, a(n) for n = 1..10000

EXAMPLE

For n = 1 we have A001358(n) = 4, A001358(n+1) = 6; there is no k such that 6 - 4 = 2 = (4 mod k), hence a(1) = 0.

For n = 3 we have A001358(n) = 9, A001358(n+1) = 10; 8 is the largest k such that 10 - 9 = 1 = (9 mod k), hence a(3) = 8; a(3) = A001358(3) - A065516(3) = 8.

For n = 20 we have A001358(n) = 57, A001358(n+1) = 58; 56 is the largest k such that 58 - 57 = 1 = (57 mod k), hence a(20) = 56; a(20) = A001358(20) - A065516(20) = 56.

CROSSREFS

Cf. A001358, A065516, A130533, A184729, A117078, A117563, A001223, A118534.

Sequence in context: A303316 A340518 A173435 * A119876 A281718 A036176

Adjacent sequences: A184725 A184726 A184727 * A184729 A184730 A184731

KEYWORD

nonn,easy

AUTHOR

Rémi Eismann, Jan 20 2011

STATUS

approved