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 A112877 Zeros in Cald's sequence: positions n such that A006509(n) = 0. 4
 117, 199, 381, 427, 521, 721, 1151, 1997, 3625, 6607, 12269, 23209, 41133, 75441, 141209, 266969, 507701, 968373, 1851971, 3549473, 6817481, 13115259, 25267949, 48750929, 94173137, 182122379 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS EXAMPLE A006509(117) = 0 and A006509(k) > 0 for k < 117, so a(1) = 117. MATHEMATICA a[1] = 1; a[n_] := a[n] = Block[{b = a[n - 1], p = Prime[n - 1]}, If[ b - p > 0 && Position[t, b - p] == {}, b - p, If[ Position[t, b + p] == {}, b + p, 0]]]; t = {1}; Do[ AppendTo[t, a[n]], {n, 2, 270000}]; Flatten[ Position[t, 0]] (* Robert G. Wilson v *) CROSSREFS Cf. A006509, A112878, A117128, A117129. Sequence in context: A272389 A201021 A187990 * A064180 A050245 A031174 Adjacent sequences:  A112874 A112875 A112876 * A112878 A112879 A112880 KEYWORD nonn AUTHOR Klaus Brockhaus, Oct 24 2005 EXTENSIONS a(15) and a(16) from Robert G. Wilson v, Oct 29 2005 a(17) and a(18) from Klaus Brockhaus, Jan 01 2006 a(19)-a(26) from Donovan Johnson, Feb 18 2010 STATUS approved

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