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 A100973 #16 Jul 01 2025 02:49:21 %S A100973 15540,21054,25331,44360,44660,44733,47652,50560,54944,76857,77142, %T A100973 83334,83694,96448,97944,106575,108273,117624,125952,138966,141204, %U A100973 144236,153318,158417,159424,188529,188598,189350,192000,192126,196652,202350,203320,205390,246675,247632 %N A100973 Integers that are Rhonda numbers to base 9. %C A100973 See sequence A099542 for definition of Rhonda numbers and for some links. %H A100973 Reinhard Zumkeller, <a href="/A100973/b100973.txt">Table of n, a(n) for n = 1..1000</a> %H A100973 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/RhondaNumber.html">Rhonda Number</a> %e A100973 The product of the base 9 digits of 15540 is 2*3*2*7*6=504, the sum of the prime factors of 15540 is 2*2+3+5+7+37=56 and 504=9*56. So 15540 is a Rhonda number to base 9. %t A100973 A100973Q[k_] := Times @@ IntegerDigits[k, 9] == 9*Total[Times @@@ FactorInteger[k]]; %t A100973 Select[Range[250000], A100973Q] (* _Paolo Xausa_, Jul 01 2025 *) %o A100973 (Haskell) %o A100973 a100973 n = a100973_list !! (n-1) %o A100973 a100973_list = filter (rhonda 9) a255808_list %o A100973 -- Function rhonda as in A099542. %o A100973 -- _Reinhard Zumkeller_, Mar 08 2015 %Y A100973 Cf. Rhonda numbers to other bases: A100968 (base 4), A100969 (base 6), A100970 (base 8), A099542 (base 10), A100971 (base 12), A100972 (base 14), A100974 (base 15), A100975 (base 16), A255735 (base 18), A255732 (base 20), A255736 (base 30), A255731 (base 60), see also A255872. %Y A100973 Cf. A001414, A027746, A007095, subsequence of A255808. %Y A100973 Column k=4 of A291925. %K A100973 easy,nonn,base %O A100973 1,1 %A A100973 Mark Hudson (mrmarkhudson(AT)hotmail.com), Nov 25 2004