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 A180484 #24 Nov 04 2024 18:34:37
%S A180484 1,2,3,4,5,6,7,8,9,11,12,15,24,36,111,112,115,128,132,135,144,175,212,
%T A180484 216,224,312,315,384,432,612,624,672,735,816,1111,1112,1113,1114,1115,
%U A180484 1116,1121,1122,1124,1125,1127,1128,1131,1134,1144,1161,1164,1176,1184
%N A180484 Numbers n such that r*(n/k)^2 is an integer, where n=(x_1 x_2 ... x_r) with x_i the decimal digits of n and k = x_1 * x_2 * ... * x_r.
%C A180484 A007602 is a subsequence, with 1114 the first nonmember of A007602. - _D. S. McNeil_, Sep 09 2010
%H A180484 Chai Wah Wu, <a href="/A180484/b180484.txt">Table of n, a(n) for n = 1..19985</a>
%e A180484 n=36, r=2, 2*(36/3*6)^2=8, n=36 belongs to the sequence.
%p A180484 A055642 := proc(n) max(1, ilog10(n)+1) ; end proc:
%p A180484 A007954 := proc(n) mul(d, d= convert(n,base,10)) : end proc:
%p A180484 isA180484 := proc(n) r := A055642(n) ; k := A007954(n) ; if k <> 0 then type(r*n^2/k^2,'integer') ; else false; end if; end proc:
%p A180484 for n from 1 to 2200 do if isA180484(n) then printf("%d,",n) ; end if; end do:
%p A180484 # _R. J. Mathar_, Sep 08 2010
%o A180484 (Python)
%o A180484 from gmpy2 import t_mod, mpz
%o A180484 from operator import mul
%o A180484 from functools import reduce
%o A180484 A180484 = [int(mpz(n)) for n in (str(x) for x in range(1, 10**9)) if not
%o A180484 (n.count('0') or t_mod(mpz(n)**2*len(n),
%o A180484 reduce(mul, (mpz(d) for d in n))**2))]
%o A180484 # _Chai Wah Wu_, Aug 26 2014
%o A180484 (PARI) is(n)=my(d=digits(n), r=#d, k=vecprod(d)); k && denominator((n/k)^2*r)==1 \\ _Charles R Greathouse IV_, Jun 03 2020
%Y A180484 Subsequence of A052382. A007602 is a subsequence.
%K A180484 base,easy,nonn
%O A180484 1,2
%A A180484 _Ctibor O. Zizka_, Sep 07 2010
%E A180484 More terms from _R. J. Mathar_ and _D. S. McNeil_, Sep 08 2010
%E A180484 Updated an A-number in a comment _R. J. Mathar_, Oct 18 2010