A062624 Number of integers less than A000108(n) relatively prime to A000108(n).

1, 1, 1, 4, 6, 12, 40, 240, 480, 1920, 6912, 20736, 76032, 253440, 608256, 4257792, 7983360, 26611200, 88704000, 319334400, 1277337600, 5109350400, 19508428800, 73156608000, 336520396800, 1177821388800, 6281714073600, 23332080844800, 66663088128000

Offset

0,4

Links

Harry J. Smith, Table of n, a(n) for n = 0..200

Florian Luca, Pantelimon Stanica, On the Euler function of the Catalan numbers, Journal of Number Theory 132(7):1404-1424, July 2012.

Formula

a(n) = phi(binomial(2n, n)/(n+1)).

a(n) = A000010(A000108(n)).

Maple

with(numtheory): a:= n-> phi(binomial(2*n, n)/(n+1)): seq(a(n), n=0..27); # Zerinvary Lajos, Oct 05 2007

Prog

(PARI) a(n) = eulerphi(binomial(2*n, n)/(n + 1));
(Sage) [euler_phi(binomial(2*n, n)/(n+1))for n in range(0, 28)] # Zerinvary Lajos, Jun 06 2009

Crossrefs

Cf. A000010, A000108.

Sequence in context: A242211 A073167 A060202 * A154666 A050537 A114413

Adjacent sequences: A062621 A062622 A062623 * A062625 A062626 A062627

Keyword

easy,nonn

Author

Jason Earls, Jul 04 2001

Status

approved