A078261 a(n) = numerator(N) where N = 0.246...(2n) is the concatenation of the first n even numbers after the decimal point.

1, 6, 123, 617, 24681, 6170253, 1234050607, 30851265177, 12340506070809, 123405060708091, 123405060708091011, 1542563258851137639, 1234050607080910111213, 61702530354045505560657, 2468101214161820222426283, 308512651770227527803285379, 123405060708091011121314151617

Offset: 1

Author

Amarnath Murthy, Nov 24 2002

Keywords

• base
• nonn

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..351

Crossrefs

Cf. A078258 (similar, with concatenation of 1 to n), A078260 (denominators).

Programs

Maple

a:= n-> (t-> numer(t/10^length(t)))(parse(cat(2*i$i=1..n))):
seq(a(n), n=1..17);  # Alois P. Heinz, Jun 25 2025

PARI

a(n) = {my(s = ""); for (k=1, n, s = concat(s, Str(2*k))); numerator(eval(s)/10^(#s));} \\ Michel Marcus, Jan 15 2019

Extensions

More terms from Antonio G. Astudillo (afg_astudillo(AT)lycos.com), Apr 19 2003

More terms from Michel Marcus, Jan 15 2019