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 A117799 #9 Mar 27 2024 09:15:47 %S A117799 0,1,7337,12692,19505,37505,61337,75440,146432,240752,326801,358400, %T A117799 620417,708401,802217,851312,1007345,1062272,1176500,1235801,1422452, %U A117799 1622225,1835120,1909001,2061137,2219105,2300276,2728001,4010672,4803401,5043017,5165012,7026032,7315220,7462001 %N A117799 Icosagonal numbers for which the sum of the digits is also an icosagonal number. %e A117799 7337 is in the sequence because (1) it is an icosagonal number and (2) the sum of the digits 7+3+3+7=20 is also an icosagonal number. %o A117799 (PARI) isok(n) = ispolygonal(n, 20) && ispolygonal(sumdigits(n), 20); \\ _Michel Marcus_, Feb 27 2014 %Y A117799 Cf. A007953, A051872. %K A117799 nonn,base %O A117799 1,3 %A A117799 Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006 %E A117799 a(11) corrected by _Georg Fischer_, Mar 27 2024