A077576 a(1) = 1; for n > 1, a(n) = largest prime divisor of A062273(n).

1, 23, 19, 263, 823, 678901, 50993, 1279, 211, 150866941, 353594393, 757819, 9012345678901, 213408443, 11904282563, 435503, 21339439879, 7403356241, 13212859242013, 27961, 205126079, 5201061865265117273, 54843374833199, 1384232185401581113277, 12792129877

Offset: 1

Author

Amarnath Murthy, Nov 11 2002

Keywords

• base
• nonn

Links

• Daniel Suteu, Table of n, a(n) for n = 1..131

Crossrefs

Cf. A006530, A062273.

Programs

PARI

f(n) = sum(i=1, n, ((n*(n-1)/2+i) % 10)*10^(n-i)); \\ A062273
a(n) = my(x=f(n)); if (x==1, 1, vecmax(factor(x)[,1])); \\ Michel Marcus, May 26 2022

Formula

a(n) = A006530(A062273(n)). - Michel Marcus, May 26 2022

Extensions

More terms from Sascha Kurz, Jan 12 2003

a(24)-a(25) from Daniel Suteu, May 25 2022