cp's OEIS Frontend

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.

A376254 Numbers k such that A376294(k) < k.

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%I A376254 #39 Oct 26 2024 22:58:30
%S A376254 32,64,81,121,125,128,169,243,256,289,343,361,512,529,625,729,841,864,
%T A376254 961,972,1024,1152,1250,1296,1331,1369,1458,1536,1600,1681,1728,1849,
%U A376254 1875,1944,2000,2025,2048,2187,2197,2209,2304,2401,2500,2560,2592,2662,2744,2809,2916,3087,3125,3136
%N A376254 Numbers k such that A376294(k) < k.
%C A376254 There are infinitely many numbers in this sequence, since the growth of powers of small primes far outpaces the growth of their digits when concatenated.
%C A376254 First differs from A195330 at 320 which is a term there but not here.
%H A376254 Haines Hoag, <a href="/A376254/b376254.txt">Table of n, a(n) for n = 1..20000</a>
%e A376254 32 is a term since 32=2^5 and 25<32.
%e A376254 1152 is a term since 1152=2^7*3^2 and 27*32=864, and 864<1152.
%t A376254 f[p_, e_] := 10^IntegerLength[e]*p + e; q[1] = False; q[k_] := Times @@ f @@@ FactorInteger[k] < k; Select[Range[3200], q] (* _Amiram Eldar_, Sep 26 2024 *)
%o A376254 (Python)
%o A376254 from math import prod
%o A376254 from sympy import factorint
%o A376254 def ok(n): return prod(int(str(p)+str(e)) for p, e in factorint(n).items()) < n
%o A376254 print([k for k in range(1, 3200) if ok(k)]) # _Michael S. Branicky_, Sep 27 2024
%Y A376254 Cf. A376294, A195330.
%K A376254 nonn,base
%O A376254 1,1
%A A376254 _Haines Hoag_, Sep 17 2024