The On-Line Encyclopedia of Integer Sequences (OEIS)

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A328413 revision #3

A328413

Numbers k such that (Z/mZ)* = C_2 X C_(2k) has solutions m, where (Z/mZ)* is the multiplicative group of integers modulo m.

1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 14, 15, 16, 18, 20, 21, 22, 23, 24, 26, 27, 29, 30, 32, 33, 35, 36, 39, 40, 41, 42, 44, 45, 46, 48, 50, 51, 53, 54, 55, 56, 58, 60, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 78, 81, 82, 83, 86, 87, 88, 89, 90, 95, 96, 98, 99, 102, 105, 106, 110, 111

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..71.

PROG

(PARI) isA328413(n) = my(r=4*n, N=floor(exp(Euler)*r*log(log(r^2))+2.5*r/log(log(r^2)))); for(k=r+1, N+1, if(eulerphi(k)==r && lcm(znstar(k)[2])==r/2, return(1)); if(k==N+1, return(0)))

for(n=1, 100, if(isA328413(n), print1(n, ", ")))

CROSSREFS

Sequence in context: A220506 A045546 A050026 * A174788 A129143 A039225

Adjacent sequences: A328410 A328411 A328412 * A328414 A328415 A328416

KEYWORD

nonn

AUTHOR

Jianing Song, Oct 14 2019

STATUS

editing