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 A121733 Numbers n such that tau(n) = tau(n+1) mod 691, where tau is Ramanujan's tau function A000594. 7
 184, 2103, 3421, 3638, 4342, 5181, 6029, 6233, 8323, 8628, 8721, 9658, 9905, 11322, 11774, 11888, 12410, 12774, 12811, 13063, 13484, 14744, 14906, 15065, 15247, 16581, 16610, 18248, 18396, 18703, 19514, 20476, 20479, 21657, 22089, 22984 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Corresponding Ramanujan tau numbers mod 691 are listed in A121734(n) = A046694(a(n)). A121734 begins 483, 209, 21, 632, 650, 541, 546, 281, 666, 440, 397, 576, 18, 251, 356, 207, 532, 361, 121, 642, 288, 167, 348, 505, 561, 0, 108, 166, 97, 492, 58, 255, 632, 151, 679, 185, 141, 587, 0, .... There are instances of three consecutive equal terms in A046694, with A046694(n) = A046694(n+1) = A046694(n+2). Equivalently there are consecutive equal terms a(n) = a(n+1). The first is A046694(290217) = A046694(290218) = A046694(290219) = 0. - Alexander Adamchuk, Aug 18 2006 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..2500 Eric Weisstein's World of Mathematics, Ramanujan's Tau Function. EXAMPLE a(1) = 184 because the first pair of equal consecutive numbers in A046694 is A046694(184) = A046694(185) = 483 = A121734(1). MATHEMATICA Select[Range[30000], Mod[DivisorSigma[11, #1], 691]==Mod[DivisorSigma[11, #1+1], 691]&] PROG (PARI) is(n)=(ramanujantau(n)-ramanujantau(n+1))%691==0 \\ Charles R Greathouse IV, Feb 08 2017 CROSSREFS Cf. A121734, A046694, A000594. Sequence in context: A234152 A234146 A164997 * A235250 A221931 A223117 Adjacent sequences:  A121730 A121731 A121732 * A121734 A121735 A121736 KEYWORD nonn AUTHOR Alexander Adamchuk, Aug 18 2006 STATUS approved

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Last modified January 15 20:47 EST 2019. Contains 319184 sequences. (Running on oeis4.)