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.

A295042 Numbers k such that both k and (k+1) are abundant, and neither is divisible by 3.

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%I A295042 #22 Apr 11 2021 16:14:22
%S A295042 55959128224,68972878975,91653987424,171967420624,350441716624,
%T A295042 372944997424,386136575824,711480344575,769856312224,789255692224,
%U A295042 818564922175,997039218175,1071710665024,1216042052224,1340586071824,1925671372624,1954925637664,2045947528624
%N A295042 Numbers k such that both k and (k+1) are abundant, and neither is divisible by 3.
%C A295042 Subsequence of A096399.
%C A295042 All terms are of the form 3j+1, with j = 18653042741, 22990959658, 30551329141, 57322473541, 116813905541, 124314999141, 128712191941, 237160114858, 256618770741, 263085230741, 272854974058, 332346406058, ...
%H A295042 David A. Corneth, <a href="/A295042/b295042.txt">Table of n, a(n) for n = 1..988</a> (first 87 terms from Giovanni Resta)
%e A295042 k = 55959128224 is in the sequence as sigma(k) > 2*k and sigma(k + 1) > 2*(k + 1). - _David A. Corneth_, Apr 11 2021
%t A295042 abQ[n_] := Mod[n, 3] > 0 && DivisorSigma[1, n] > 2 n; abQ1[n_] := abQ[n - 1]; abQ2[n_] := abQ[n + 1]; s = Import["b115414.txt", "Data"][[All, -1]]; s1 = Select[s, abQ1] - 1; s2 = Select[s, abQ2]; seq = Union[s1, s2] (* using the b-File from A115414 *)
%o A295042 (PARI) isoka(n) = (n%3) && (sigma(n) > 2*n);
%o A295042 isok(n) = isoka(n) && isoka(n+1); \\ _Michel Marcus_, Nov 13 2017
%Y A295042 Cf. A005101, A096399, A115414.
%K A295042 nonn
%O A295042 1,1
%A A295042 _Amiram Eldar_, Nov 13 2017
%E A295042 a(13)-a(18) from _Giovanni Resta_, Aug 22 2018