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A341811
a(n) = 1/(Sum_{k=1..n} 1/phi(A341810(n)*k)).
3
1, 1, 1, 2, 4, 8, 3, 24, 12, 3, 120, 30, 9, 45, 32, 120, 320, 160, 720, 2880, 256, 1280, 15840, 1408, 704, 2112, 3168, 9504, 88704, 199584, 221760, 133056, 8316, 22176, 22176, 76032, 57024, 19008, 1540, 19008, 23100, 138600, 55440, 3465, 14784, 64064, 239085
OFFSET
1,4
LINKS
EXAMPLE
a(2) = 1/(1/phi(3)+1/phi(6)) = 1/(1/2+1/2) = 1.
a(3) = 1/(1/phi(4)+1/phi(8)+1/phi(12)) = 1/(1/2+1/4+1/4) = 1.
a(4) = 1/(1/phi(7)+1/phi(14)+1/phi(21)+1/phi(28)) = 1/(1/6+1/6+1/12+1/12) = 2.
PROG
(PARI) a(n) = my(k=1); while (denominator(m=1/sum(j=1, n, 1/eulerphi(k*j))) != 1, k++); m;
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 20 2021
STATUS
approved