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 A072494 #25 Jun 03 2025 02:27:44
%S A072494 1880,4780,4870,7480,7839,7840,8180,8470,8739,8740,8810,10880,11248,
%T A072494 11249,11519,12148,12149,13898,15119,18080,18800,21148,21149,23308,
%U A072494 25680,25860,26580,26850,28560,28650,31898,32308,33208,33319,40780,40870,44488,44489
%N A072494 First of triples of consecutive happy numbers, i.e., the first of three consecutive integers each of which is a happy number (A007770).
%D A072494 David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 154 (Rev. ed. 1997).
%H A072494 Amiram Eldar, <a href="/A072494/b072494.txt">Table of n, a(n) for n = 1..10000</a>
%H A072494 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HappyNumber.html">Happy Number</a>
%e A072494 7480 is included because 7480, 7481 and 7482 are all happy numbers.
%t A072494 happyQ[n_] := Nest[Plus @@(IntegerDigits[ # ]^2)&, n, 50] == 1; Transpose[Select[Partition[Select[Range[50000], happyQ], 3, 1], #[[3]] - #[[2]] == #[[2]] - #[[1]] == 1 &]][[1]]
%t A072494 f[n_] := Total[IntegerDigits[n]^2]; t = Select[Range[50000], NestWhile[f, #, UnsameQ, All] == 1 &]; t[[Select[Range[Length[t] - 2], t[[#]] == t[[# + 1]] - 1 == t[[# + 2]] - 2 &]]] (* _T. D. Noe_, Aug 23 2011 *)
%t A072494 SequencePosition[Table[If[FixedPoint[Total[IntegerDigits[#]^2]&,n,100]==1,1,0],{n,45000}],{1,1,1}][[All,1]] (* _Harvey P. Dale_, Jun 19 2022 *)
%K A072494 nonn,base
%O A072494 1,1
%A A072494 _Harvey P. Dale_, Aug 02 2002