1,1

Corresponding Ramanujan tau numbers mod 691 are listed in A121743[n] = A046694[a(n)]. A121743[n] begins {0,276,91,79,0,0,...}. a(n) are the indices of the first number in the Ramanujan tau triplets mod 691. All a(n) belong to A121733[n] - indices of the first number in the Ramanujan tau twins mod 691. There are also quadruplets in the Ramanujan tau mod 691 such that A046694[n] = A046694[n+1] = A046694[n+2] = A046694[n+3]. The first such Ramanujan tau Quadruplet mod 691 starts with A046694[1409635] = 0.

Eric Weisstein Link to a section of The World of Mathematics. Ramanujan's Tau Function.

Do[f=Mod[DivisorSigma[11, n], 691]; g=Mod[DivisorSigma[11, n+1], 691]; h=Mod[DivisorSigma[11, n+2], 691]; If[f==g&&g==h, Print[{n, f}]], {n, 1, 1500000}]

Cf. A121743, A121733, A121734, A046694, A000594.

Sequence in context: A096519 A157112 A043616 this_sequence A093792 A068241 A104328

Adjacent sequences: A121739 A121740 A121741 this_sequence A121743 A121744 A121745

nonn

Alexander Adamchuk (alex(AT)kolmogorov.com), Aug 19 2006