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.
%I A028839 #41 Jul 08 2025 18:53:57 %S A028839 1,4,9,10,13,18,22,27,31,36,40,45,54,63,72,79,81,88,90,97,100,103,108, %T A028839 112,117,121,126,130,135,144,153,162,169,171,178,180,187,196,202,207, %U A028839 211,216,220,225,234,243,252,259,261,268,270,277,286,295,301,306,310 %N A028839 Sum of digits of n is a square. %C A028839 Difference between two consecutive terms is never equal to 8. - _Carmine Suriano_, Mar 31 2014 %C A028839 In this sequence, there is no number of the form 3*k-1. In other words, if a(n) is not divisible by 9, it must be of the form 3*k+1. - _Altug Alkan_, Apr 08 2016 %H A028839 Carmine Suriano, <a href="/A028839/b028839.txt">Table of n, a(n) for n = 1..1242</a> %e A028839 234511 belongs to the sequence as its sum of digits is 16, a square. %t A028839 Select[ Range[ 500 ], IntegerQ[ Sqrt[ Apply[ Plus, IntegerDigits[ # ] ] ] ]& ] %o A028839 (Magma) [n: n in [1..400] | IsSquare(&+Intseq(n))]; // _Bruno Berselli_, May 26 2011 %o A028839 (PARI) isok(n) = issquare(sumdigits(n)); \\ _Michel Marcus_, Oct 30 2014 %Y A028839 Cf. A007953, A028837, A050626. %Y A028839 Cf. A053057 (squares whose digit sum is also a square). %K A028839 nonn,base,easy %O A028839 1,2 %A A028839 _N. J. A. Sloane_ %E A028839 More terms from _Erich Friedman_