A115208 a(1)=0. a(n) = number of earlier terms of the sequence which when added to n produce a composite number.

0, 0, 0, 3, 1, 4, 2, 6, 6, 7, 4, 9, 5, 10, 11, 12, 9, 14, 11, 14, 18, 17, 14, 20, 18, 20, 17, 23, 18, 22, 22, 26, 23, 29, 26, 26, 26, 30, 28, 36, 23, 34, 30, 34, 31, 43, 30, 40, 33, 37, 43, 45, 31, 46, 42, 44, 40, 48, 42, 48, 39, 52, 47, 53

Offset

1,4

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

Example

Adding 7 to the first 6 terms of the sequence gives [7,7,7,10,8,11]. Of these terms, two are composite, so a(7) = 2.

Mathematica

a = {0, 0}; For[n = 3, n < 90, n++, in = 0; For[j = 1, j < Length[a] + 1, j++, If[ ! PrimeQ[n + a[[j]]], in++ ]]; AppendTo[a, in]]; a (* Stefan Steinerberger, Jun 03 2007 *)

Crossrefs

Cf. A115207, A115209, A115210.

Sequence in context: A139432 A363653 A202154 * A234930 A351887 A273261

Adjacent sequences: A115205 A115206 A115207 * A115209 A115210 A115211

Keyword

nonn

Author

Leroy Quet, Jan 16 2006

Extensions

More terms from Stefan Steinerberger, Jun 03 2007

Status

approved