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 A194352 #17 Feb 16 2025 08:33:15 %S A194352 7839,8739,11248,12148,21148,44488,44489,44939,49439,70839,78039, %T A194352 80739,87039,94439,101248,102148,110248,112048,120148,121048,201148, %U A194352 210148,211048,222688,222689,226288,226289,236839,238639,258598,258599,262288,262289,263839 %N A194352 First of quadruples of consecutive happy numbers. %H A194352 Amiram Eldar, <a href="/A194352/b194352.txt">Table of n, a(n) for n = 1..10000</a> %H A194352 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HappyNumber.html">Happy Number</a>. %e A194352 7839, 7840, 7841, 7842 are the first of four consecutive integers each of which is a happy number, hence a(1) = 7839. %t A194352 f[n_] := Total[IntegerDigits[n]^2]; t = Select[Range[300000], NestWhile[f, #, UnsameQ, All] == 1 &]; t[[Select[Range[Length[t] - 3], t[[#]] == t[[# + 1]] - 1 == t[[# + 2]] - 2 == t[[# + 3]] - 3 &]]] (* _T. D. Noe_, Aug 22 2011 *) %Y A194352 Cf. A007770, A035502, A055629, A072494. %K A194352 nonn,base %O A194352 1,1 %A A194352 _Martin Renner_, Aug 22 2011