A153848 Repeat 21.

21, 2121, 212121, 21212121, 2121212121, 212121212121, 21212121212121, 2121212121212121, 212121212121212121, 21212121212121212121, 2121212121212121212121, 212121212121212121212121, 21212121212121212121212121, 2121212121212121212121212121

Offset

1,1

Links

Table of n, a(n) for n=1..14.

Index entries for linear recurrences with constant coefficients, signature (101,-100).

Formula

a(n) = (10^(2*n)-1)*21/99.

Maple

a:= n-> parse(cat(21$n)):
seq(a(n), n=1..20);  # Alois P. Heinz, Jun 16 2021

Prog

(PARI) g2(n) = (10^(2*n)-1)*1*21/99 for(x=1, 25, print1(g2(x), ", "))

Crossrefs

Cf. A177090.

Sequence in context: A265175 A300577 A304643 * A221771 A007593 A369097

Adjacent sequences: A153845 A153846 A153847 * A153849 A153850 A153851

Keyword

nonn,easy

Author

Cino Hilliard, Jan 02 2009

Status

approved