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A115208 a(1)=0. a(n) = number of earlier terms of the sequence which when added to n produce a composite number. 4
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 (list; graph; refs; listen; history; text; internal format)
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: A309650 A139432 A202154 * A234930 A273261 A274531

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

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)