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 A224401 #24 Oct 30 2023 11:07:08 %S A224401 1,2,2,3,4,5,4,6,3,5,4,7,4,5,5,8,9,7,9,7,5,10,9,11,3,10,6,7,9,12,9,13, %T A224401 10,10,10,14,9,10,10,11,9,12,9,7,7,10,9,15,16,7,10,17,18,11,10,11,19, %U A224401 19,18,20,18,19,17,21,19,12,18,17,19,12,18,22,18,19 %N A224401 a(n) is the row number of triangle A085612 in which n appears. %C A224401 Row number in A085612 triangle of prime signatures. %C A224401 a(n) is not the same for all numbers n with the same prime signature. For such a sequence, see A101296. - _Peter Munn_, Oct 23 2023 %H A224401 Rémy Sigrist, <a href="/A224401/b224401.txt">Table of n, a(n) for n = 1..10000</a> (first 150 terms from Matthew Goers) %H A224401 Rémy Sigrist, <a href="/A224401/a224401.gp.txt">PARI program for A224401</a> %e A224401 a(9) = 3, because 9 is in the 3rd row (1st 3 prime^2) of A085612. %e A224401 a(10) = 5, because 10 is in the 5th row (1st 5 semiprimes) of A085612. %e A224401 a(11) = 4, because 11 is in the 4th row (4 primes, prime(3)..prime(6)) of A085612. %o A224401 (Haskell) %o A224401 import Data.List (findIndex); import Data.Maybe (fromJust) %o A224401 a224401 = (+ 1) . fromJust . (`findIndex` a085612_tabf) . elem %o A224401 -- _Reinhard Zumkeller_, Jun 05 2013 %o A224401 (PARI) See Links section. %Y A224401 Cf. A085612, A101296. %Y A224401 First and last positions of each number: A085834, A085836. %K A224401 nonn %O A224401 1,2 %A A224401 _Matthew Goers_, Apr 05 2013