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A062624 Number of integers less than A000108(n) relatively prime to A000108(n). 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 1 04:05 EDT 2022. Contains 357134 sequences. (Running on oeis4.)