A341810 a(n) is the least integer k such that 1/(Sum_{j=1..n} 1/phi(k*j)) is an integer.

1, 3, 4, 7, 22, 31, 24, 101, 53, 22, 563, 149, 75, 321, 310, 653, 3110, 907, 5926, 16829, 2505, 12735, 96179, 12969, 5931, 18033, 20231, 61483, 579559, 1323199, 1477613, 1133209, 65051, 151643, 152567, 610799, 459949, 154553, 17006, 156863, 285170

Offset

1,2

Links

Seiichi Manyama, Table of n, a(n) for n = 1..55

Prog

(PARI) a(n) = my(k=1); while (denominator(1/sum(j=1, n, 1/eulerphi(k*j))) != 1, k++); k; \\ Michel Marcus, Feb 20 2021

Crossrefs

Inspired by A341799.

Cf. A000010, A341811, A341813.

Sequence in context: A030724 A124082 A056655 * A338511 A332971 A292033

Adjacent sequences: A341807 A341808 A341809 * A341811 A341812 A341813

Keyword

nonn

Author

Seiichi Manyama, Feb 20 2021

Status

approved