A325571 - OEIS

A325571

Composite numbers n that have no divisor d > 1 such that A048720(A065621(d),n/d) = n.

15, 25, 27, 39, 51, 55, 57, 63, 69, 77, 81, 85, 87, 91, 95, 99, 111, 115, 117, 119, 121, 123, 125, 141, 143, 145, 147, 159, 169, 171, 175, 177, 183, 185, 187, 201, 203, 205, 207, 209, 213, 215, 219, 221, 231, 235, 237, 243, 245, 247, 249, 253, 255, 261, 265, 267, 275, 285, 287, 289, 291, 295, 299, 301, 303, 305, 319, 321

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OFFSET

1,1

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..10000

PROG

(PARI)

A048720(b, c) = fromdigits(Vec(Pol(binary(b))*Pol(binary(c)))%2, 2);

A065621(n) = bitxor(n-1, n+n-1);

isA325571(n) = ((n>1)&&!isprime(n)&&fordiv(n, d, if(A048720(A065621(n/d), d)==n, return(d==n))));

CROSSREFS

Cf. A048720, A065621, A325573.