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 A179782 #19 Mar 24 2020 05:02:50
%S A179782 0,1,5,7,25,67,482,551,625,667,2937,6667,9284,9376,9649,48179,49900,
%T A179782 55712,66667,89517,90625,161579,631206,666667,890625,1348613,2089517,
%U A179782 3863187,4999000,6666667,7109376,7477735,8575619,10721030,12890625
%N A179782 Numbers n such that the decimal representation of n is contained as substring in that of the n-th pentagonal number.
%C A179782 This is to pentagonal numbers A000326 as A119238 is to triangular numbers A000217 and as A018834 is to squares A000290. All numbers of the form (10^n-1)/3*2+1 are contained in this list {1, 7, 67, 667, 6667, 66667, 666667, 6666667, 66666667, ...} _Alois P. Heinz_. Extension: Values 8-25 by _Claudio Meller_, 26-37 by _D. S. McNeil_.
%e A179782 The 5th pentagonal number, 35, which contains 5.
%e A179782 The 7th pentagonal number, 70, which contains 7.
%e A179782 The 25th pentagonal number, 925, which contains 25.
%e A179782 The 67th pentagonal number, 6700, which contains 67.
%e A179782 The 482nd pentagonal number, 348245, which contains 482.
%e A179782 The 667th pentagonal number, 667000, which contains 667.
%o A179782 (Sage) [n for n in range(10**4) if str(n) in str((3*n**2-n)//2)]
%Y A179782 Cf. A000217, A000290, A000326, A018834, A067275, A119238.
%K A179782 base,nonn
%O A179782 1,3
%A A179782 _Jonathan Vos Post_, Jul 27 2010
%E A179782 Code clarified by _D. S. McNeil_, Aug 08 2010