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.

A309884 Numbers k such that A003132(k^3) = A003132(k), where A003132(n) is the sum of the squares of the digits of n.

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%I A309884 #27 Sep 08 2022 08:46:22
%S A309884 0,1,10,74,100,740,1000,3488,7400,10000,23658,30868,34880,47508,48517,
%T A309884 52187,58947,59468,67685,68058,74000,76814,78368,78845,84878,100000,
%U A309884 108478,145877,149217,163871,179685,186884,188647,218977,219878,236580,238758,248967,278638,292597,308680
%N A309884 Numbers k such that A003132(k^3) = A003132(k), where A003132(n) is the sum of the squares of the digits of n.
%C A309884 If k is in the sequence, then so are k*10^r, with r >= 1.
%e A309884 74^3 = 405224, A003132(74) = 7^2 + 4^2 = 65, A003132(405224) = 4^2 + 0^2 + 5^2 + 2^2 + 2^2 + 4^2 = 65.
%t A309884 digSum[n_] := Total[IntegerDigits[n]^2]; Select[Range[0, 310000], digSum[#] == digSum[#^3] &] (* _Amiram Eldar_, Aug 22 2019 *)
%o A309884 (PARI) for(i = 0, 400000, if(norml2(digits(i^3)) == norml2(digits(i)), print1(i, ", ")))
%o A309884 (Magma) [0] cat [k:k in [1..310000]| &+[c^2: c in Intseq(k)] eq &+[c^2: c in Intseq(k^3)]]; // _Marius A. Burtea_, Aug 26 2019
%Y A309884 Cf. A003132, A058369, A070276, A174460, A176670, A178213, A307735, A309883.
%K A309884 nonn,base
%O A309884 1,3
%A A309884 _Antonio Roldán_, Aug 21 2019