

A130767


a(n) = product{k=1 to n} (kth integer from among those positive integers which are coprime to (n+1k)).


1



1, 2, 9, 40, 420, 2700, 56595, 419328, 8820900, 88488400, 2327925600, 38767286880, 1912404574080, 21612951360000, 644047087612500, 10985391056640000, 634391869996684800, 14046187624838328960, 764077915447610400000, 15840110879873280000000, 755098009918296312668400
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

a(n) is the product of the terms in the nth antidiagonal of the A126572 array.  Michel Marcus, Mar 14 2018


LINKS

Table of n, a(n) for n=1..21.


EXAMPLE

The integers coprime to 1 are: 1,2,3,4,5,6,... The 5th of these is 5. The integers coprime to 2 are: 1,3,5,7,9,... The 4th of these is 7. The integers coprime to 3 are: 1,2,4,5,7,... The 3rd of these is 4. The integers coprime to 4 are: 1,3,5,... The 2nd of these is 3. And the integers coprime to 5 are: 1,2,3,4,6,... The first of these is 1. So a(5) = 5 * 7 * 4 * 3 * 1 = 420.


PROG

(PARI) cop(k, j) = {my(nbc = 0, i = 0); while (nbc != j, i++; if (gcd(i, k)==1, nbc++)); i; }
a(n) = {my(vc = vector(n, k, cop(k, nk+1))); prod(k=1, n, vc[k]); } \\ Michel Marcus, Mar 14 2018


CROSSREFS

Cf. A126572, A132273, A132421.
Sequence in context: A002825 A259339 A052322 * A273461 A217190 A020698
Adjacent sequences: A130764 A130765 A130766 * A130768 A130769 A130770


KEYWORD

nonn


AUTHOR

Leroy Quet, Aug 18 2007


EXTENSIONS

More terms from Michel Marcus, Mar 14 2018


STATUS

approved



