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

0, 1, 10, 74, 100, 740, 1000, 3488, 7400, 10000, 23658, 30868, 34880, 47508, 48517, 52187, 58947, 59468, 67685, 68058, 74000, 76814, 78368, 78845, 84878, 100000, 108478, 145877, 149217, 163871, 179685, 186884, 188647, 218977, 219878, 236580, 238758, 248967, 278638, 292597, 308680

Offset

1,3

Comments

If k is in the sequence, then so are k*10^r, with r >= 1.

Links

Table of n, a(n) for n=1..41.

Example

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.

Mathematica

digSum[n_] := Total[IntegerDigits[n]^2]; Select[Range[0, 310000], digSum[#] == digSum[#^3] &] (* Amiram Eldar, Aug 22 2019 *)

Prog

(PARI) for(i = 0, 400000, if(norml2(digits(i^3)) == norml2(digits(i)), print1(i, ", ")))
(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

Crossrefs

Cf. A003132, A058369, A070276, A174460, A176670, A178213, A307735, A309883.

Sequence in context: A199556 A044197 A044578 * A279284 A264082 A103434

Adjacent sequences: A309881 A309882 A309883 * A309885 A309886 A309887

Keyword

nonn,base

Author

Antonio Roldán, Aug 21 2019

Status

approved