cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A343137 Positions of records in A188172.

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%I A343137 #14 Apr 09 2021 09:25:21
%S A343137 1,7,63,315,945,1575,3465,10395,17325,26775,45045,135135,225225,
%T A343137 405405,675675,1576575,2027025,2297295,3828825,6891885,11486475,
%U A343137 26801775,34459425,43648605,72747675,130945815,218243025,509233725,654729075,1003917915,1527701175,3011753745,4583103525
%N A343137 Positions of records in A188172.
%e A343137 945 is in the sequence as A188172(945) = 4 via the divisors 7, 15, 63 and 135 and no positive integer < 945 has at least four such (7 (mod 8)) divisors.
%t A343137 Function[{s, r}, Map[FirstPosition[s, #][[1]] &, r]] @@ {#, Union@ FoldList[Max, #]} &@ Array[DivisorSum[#, 1 &, Mod[#, 8] == 7 &] &, 10^6] (* _Michael De Vlieger_, Apr 08 2021 *)
%Y A343137 Cf. A188172, A188226.
%K A343137 nonn
%O A343137 1,2
%A A343137 _David A. Corneth_, Apr 06 2021