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 A378139 #42 Jan 29 2025 13:13:54 %S A378139 2,3,23,11,19,263,167,103,487,1039,7951,5903,28319,107071,67231, %T A378139 590399,180799,344639,1480319,12181759,4757119,10871039,1611391, %U A378139 140167679,203082239,228248063,530237951,1812718591,5302379519,13295347711,12758476799,132953477119,1410065407 %N A378139 Smallest prime number such that the number of distinct prime factors with multiplicity of its 9's complement is equal to n. If no such number exists, return -1. %H A378139 Michael S. Branicky, <a href="/A378139/b378139.txt">Table of n, a(n) for n = 1..1000</a> (terms 1..37 from Jean-Marc Rebert) %e A378139 2 is prime, 9-2 = 7 and bigomega(7) = 1. %o A378139 (PARI) nc(n) = my(e=length(Str(n))); 10^e-1 - n; \\ A061601 %o A378139 a(n) = my(p=2); while (bigomega(nc(p)) != n, p = nextprime(p+1)); p; \\ _Michel Marcus_, Jan 08 2025 %Y A378139 Cf. A000040, A001221, A001222, A061601. A377471, %K A378139 nonn,base %O A378139 1,1 %A A378139 _Jean-Marc Rebert_, Jan 08 2025