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.

A174456 Numbers k such that d(k) = d(k+1) = 12.

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%I A174456 #12 Dec 23 2021 21:49:23
%S A174456 735,819,1035,1196,1274,1275,1449,1665,1924,1925,1952,1988,2324,2331,
%T A174456 2540,2655,3068,3195,3267,3324,3339,3549,3555,3626,3717,4164,4220,
%U A174456 4235,4556,4563,4598,4635,4675,4796,5024,5084,5324,5525,5588,5634,5660,6003
%N A174456 Numbers k such that d(k) = d(k+1) = 12.
%H A174456 Zak Seidov, <a href="/A174456/b174456.txt">Table of n, a(n) for n = 1..71998</a>
%e A174456 a(1) =  735 = A030630(67)  = A030630(68)  - 1 = A005237(88);
%e A174456 a(2) =  819 = A030630(76)  = A030630(77)  - 1 = A005237(99);
%e A174456 a(3) = 1035 = A030630(100) = A030630(101) - 1 = A005237(124).
%t A174456 Select[Range[10^7],DivisorSigma[0,{#,#+1}]=={12,12}&]
%t A174456 Transpose[SequencePosition[DivisorSigma[0,Range[6500]],{12,12}]][[1]] (* The program uses the SequencePosition function from Mathematica version 10 *) (* _Harvey P. Dale_, Jul 16 2016 *)
%o A174456 (PARI) is(n)=numdiv(n)==12 && numdiv(n+1)==12 \\ _Charles R Greathouse IV_, Jun 19 2016
%Y A174456 Intersection of A005237 and A030630.
%K A174456 nonn
%O A174456 1,1
%A A174456 _Zak Seidov_, May 25 2010