A077576 - OEIS

%I #15 May 26 2022 07:04:18

%S 1,23,19,263,823,678901,50993,1279,211,150866941,353594393,757819,

%T 9012345678901,213408443,11904282563,435503,21339439879,7403356241,

%U 13212859242013,27961,205126079,5201061865265117273,54843374833199,1384232185401581113277,12792129877

%N a(1) = 1; for n > 1, a(n) = largest prime divisor of A062273(n).

%H Daniel Suteu, <a href="/A077576/b077576.txt">Table of n, a(n) for n = 1..131</a>

%F a(n) = A006530(A062273(n)). - _Michel Marcus_, May 26 2022

%o (PARI) f(n) = sum(i=1, n, ((n*(n-1)/2+i) % 10)*10^(n-i)); \\ A062273

%o a(n) = my(x=f(n)); if (x==1, 1, vecmax(factor(x)[,1])); \\ _Michel Marcus_, May 26 2022

%Y Cf. A006530, A062273.

%K base,nonn

%O 1,2

%A _Amarnath Murthy_, Nov 11 2002

%E More terms from _Sascha Kurz_, Jan 12 2003

%E a(24)-a(25) from _Daniel Suteu_, May 25 2022