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 A269850 a(n) = number of integers k <= n for which prime(k+1)-prime(k) is a multiple of three. 5
 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 2, 2, 2, 3, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 10, 10, 11, 12, 12, 12, 12, 12, 12, 13, 14, 14, 14, 14, 15, 15, 15, 16, 17, 18, 18, 19, 19, 19, 19, 19, 19, 19, 19, 19, 20, 20, 20, 20, 21, 21, 22, 23, 23, 24, 24, 24, 24, 24, 24, 24, 24, 25, 25, 26, 26, 26, 26, 26, 27 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,11 COMMENTS a(n) = number of terms of A270190 <= n, the least monotonic left inverse of A270190. See comments at A269364. LINKS Antti Karttunen, Table of n, a(n) for n = 1..10000 Terence Tao, Biases between consecutive primes, blog entry March 14, 2016 FORMULA Other identities. For all n >= 1: a(A270190(n)) = n. MATHEMATICA Table[Count[Select[Range@ 125, Divisible[Prime[# + 1] - Prime@ #, 3] &], k_ /; k <= n], {n, 91}] (* Michael De Vlieger, Mar 17 2016 *) PROG (Scheme, with Antti Karttunen's IntSeq-library) (define A269850 (LEFTINV-LEASTMONO 1 1 A270190)) (PARI) a(n) = sum(k=1, n, ((prime(k+1) - prime(k)) % 3) == 0); \\ Michel Marcus, Mar 18 2016 CROSSREFS Cf. A270190, A269849, A269364. Sequence in context: A035450 A234537 A029126 * A036054 A029102 A241086 Adjacent sequences: A269847 A269848 A269849 * A269851 A269852 A269853 KEYWORD nonn AUTHOR Antti Karttunen, Mar 16 2016 STATUS approved

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Last modified September 10 00:26 EDT 2024. Contains 375769 sequences. (Running on oeis4.)