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 A115210 a(0)=0. a(n) = number of earlier terms of the sequence which when added to n produce a composite number. 4
 0, 0, 0, 0, 4, 1, 5, 2, 7, 7, 7, 6, 7, 7, 13, 13, 8, 11, 13, 14, 19, 19, 14, 15, 13, 23, 23, 23, 20, 21, 16, 25, 28, 27, 21, 32, 24, 29, 30, 31, 24, 32, 34, 33, 38, 37, 29, 35, 34, 43, 41, 43, 38, 43, 35, 47, 46, 49, 44, 44, 35, 54, 52, 52, 49, 52, 42, 55, 56, 55, 56, 57, 54, 59 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 LINKS G. C. Greubel, Table of n, a(n) for n = 0..10000 EXAMPLE Adding 6 to the first 6 terms (terms 0 through 5) of the sequence gives [6,6,6,6,10,7]. Of these terms, five are composite, so a(6) = 5. MATHEMATICA a = {0, 0, 0, 0}; For[n = 4, n < 10001, n++, in = 0; For[j = 1, j < Length[a] + 1, j++, If[! PrimeQ[n + a[[j]]], in++]]; AppendTo[a, in]]; a (* G. C. Greubel, Feb 05 2016 *) PROG (PARI) seq=vector(200); print1(0, ", "); for(j=1, 190, count=0; for(k=0, j-1, if(isprime(j+seq[k+1])==0 && (j+seq[k+1])>1, count=count+1; )); seq[j+1]=count; print1(seq[j+1], ", ")) \\ Matthew Conroy, Feb 07 2006 CROSSREFS Cf. A115207, A115208, A115209. Sequence in context: A168230 A080414 A067061 * A199150 A329215 A214892 Adjacent sequences:  A115207 A115208 A115209 * A115211 A115212 A115213 KEYWORD nonn AUTHOR Leroy Quet, Jan 16 2006 EXTENSIONS More terms from Matthew Conroy, Feb 07 2006 STATUS approved

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Last modified August 3 03:52 EDT 2021. Contains 346435 sequences. (Running on oeis4.)