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 A354430 #27 Jul 23 2022 19:23:50 %S A354430 1,7,22,58,142,334,766,1726,3837,8435,18364,39646,84986,181117,384160, %T A354430 811676,1709425,3590213,7522354,15728427,32827027,68405533,142344708, %U A354430 295824870,614046159,1273068141,2636250146,5452584131,11264148401,23242423457,47903544728 %N A354430 First diagonal of an array, generated from the sequence of the nonprimes. %C A354430 Mirroring the idea in A048457, here with nonprimes, and including 1 of the first generation. %C A354430 We write down the sequence of the nonprimes 1, 4, 6, ... in the first row of the array. Nonprime(k) + nonprime(k+2) will generate the second row. Thereafter we generate the further rows in a similar manner. The leftmost diagonal gives the sequence. %H A354430 Michael S. Branicky, <a href="/A354430/b354430.txt">Table of n, a(n) for n = 1..3311</a> %e A354430 1 4 6 8 9 10 12 14 15 16 18 20 21 ... %e A354430 7 12 15 18 21 24 27 30 33 36 39 ... %e A354430 22 30 36 42 48 54 60 66 72 ... %e A354430 58 72 84 96 108 120 132 ... %e A354430 142 168 192 216 240 ... %e A354430 334 384 432 ... %e A354430 766 ... %o A354430 (Python) %o A354430 from sympy import composite %o A354430 from functools import lru_cache %o A354430 @lru_cache(maxsize=None) %o A354430 def T(r, k): %o A354430 if r == 1: return 1 if k == 1 else composite(k-1) %o A354430 return T(r-1, k) + T(r-1, k+2) %o A354430 def a(n): return T(n, 1) %o A354430 print([a(n) for n in range(1, 30)]) # _Michael S. Branicky_, May 28 2022 %Y A354430 Cf. A001787, A018252, A048457, A048448, A099862. %K A354430 nonn,easy %O A354430 1,2 %A A354430 _Tamas Sandor Nagy_, May 27 2022 %E A354430 a(8) and beyond from _Michael S. Branicky_, May 28 2022