A393065 Numbers k such that A020639(k') = A053669(k) and A053669(k') = A020639(k), where k' stands for the arithmetic derivative of k, A020639 returns the least prime factor of its argument, and A053669 is the least prime not dividing its argument.

1, 6, 14, 15, 21, 26, 33, 35, 38, 39, 50, 51, 57, 62, 65, 69, 74, 86, 87, 93, 95, 110, 111, 122, 123, 129, 134, 141, 146, 155, 158, 159, 161, 170, 177, 183, 185, 194, 201, 206, 213, 215, 218, 219, 230, 237, 242, 249, 254, 267, 278, 290, 291, 302, 303, 305, 309, 314, 321, 326, 327, 330, 335, 339, 362, 365, 371, 374

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..20000

Formula

{k such that A020639(A003415(k)) == A053669(k) and A053669(A003415(k)) == A020639(k)}.

Prog

(PARI) is_A393065 = A393064;

Crossrefs

Intersection of A370125 and A391845.

Cf. A003415, A020639, A053669, A393064 (characteristic function).

Subsequence: A393066 (terms k such that k+1 is also a term).

Sequence in context: A015822 A023883 A230873 * A192321 A190272 A107982

Adjacent sequences: A393062 A393063 A393064 * A393066 A393067 A393068

Keyword

nonn,easy

Author

Antti Karttunen, Jan 31 2026

Status

approved