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 A077558 #9 Jul 01 2025 19:24:18 %S A077558 1,2,3,3,5,7,4,9,25,49,5,7,11,13,17,6,10,14,15,21,22,7,11,13,17,19,23, %T A077558 29,8,27,125,343,1331,2197,4913,6859,9,25,49,121,169,289,361,529,841, %U A077558 10,14,15,21,22,26,33,34,35,38,11,13,17,19,23,29,31,37,41,43,47,12,18,20 %N A077558 Triangle in which the n-th row contains n numbers beginning with n that have the same prime signature as n. %e A077558 1; 2,3; 3,5,7; 4,9,25,49; 5,7,11,13,17; 6,10,14,15,21,22; ... %o A077558 (Haskell) %o A077558 import Data.List (genericTake) %o A077558 a077558 n k = a077558_row n !! (k-1) %o A077558 a077558_row n = n : genericTake (n - 1) %o A077558 (filter ((== a046523 n) . a046523) [n + 1 ..]) %o A077558 a077558_tabf = map a077558_row [1..] %o A077558 -- _Reinhard Zumkeller_, Jun 05 2013 %Y A077558 Cf. A077559. %Y A077558 Cf. A046523. %K A077558 nonn,tabl %O A077558 1,2 %A A077558 _Amarnath Murthy_, Nov 10 2002 %E A077558 Corrected by Al Arnold, Jul 04 2003 %E A077558 More terms from _Ray Chandler_, Jul 17 2003