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.

A039945 Maris-McGwire numbers(2): numbers k such that f(k) = f(k+1), where f(k) = sum of digits of k + sum of digits of the distinct prime factors of k.

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%I A039945 #13 Jan 09 2021 13:29:01
%S A039945 3,12,14,45,61,118,122,124,137,143,152,213,224,225,242,273,277,356,
%T A039945 373,390,392,398,421,428,455,457,460,462,464,510,526,537,560,590,607,
%U A039945 621,673,680,692,746,782,797,804,818,820,866,878,922,939,944,965,980,985
%N A039945 Maris-McGwire numbers(2): numbers k such that f(k) = f(k+1), where f(k) = sum of digits of k + sum of digits of the distinct prime factors of k.
%H A039945 Amiram Eldar, <a href="/A039945/b039945.txt">Table of n, a(n) for n = 1..10000</a>
%t A039945 ds[n_] := Plus @@ IntegerDigits[n]; f[n_] := ds[n] + Total[ds /@ FactorInteger[n][[;; , 1]]]; s = {}; f1 = 1; Do[f2 = f[n]; If[f1 == f2, AppendTo[s, n-1]]; f1 = f2, {n, 2, 1000}]; s (* _Amiram Eldar_, Nov 24 2019 *)
%t A039945 SequencePosition[Flatten[Table[Total[IntegerDigits[n]]+Total[Flatten[IntegerDigits/@FactorInteger[n][[All,1]]]],{n,1000}]],{x_,x_}][[All,1]](* Requires Mathematica version 10 or later *) (* _Harvey P. Dale_, Jan 09 2021 *)
%Y A039945 Cf. A045759.
%K A039945 nonn,base
%O A039945 1,1
%A A039945 _David W. Wilson_