A380478 Nonprime numbers k such that A380459(k) has no divisors of form p^p.

1, 6, 14, 26, 38, 62, 74, 86, 122, 134, 146, 158, 186, 194, 206, 218, 254, 278, 302, 314, 326, 362, 386, 398, 422, 434, 446, 458, 482, 542, 554, 566, 614, 626, 662, 674, 698, 734, 746, 758, 794, 818, 842, 854, 866, 878, 906, 914, 926, 974, 998, 1046, 1082, 1094, 1142, 1154, 1202, 1214, 1226, 1238, 1262, 1266, 1286

Offset

1,2

Comments

See A380468 to find why each term must be squarefree.

After the initial 1 all terms here are even (thus in A039956) because as A276086(k) flips the parity of k, having more than one odd prime factor in k without a single 2 would make A380459(k) a multiple of 4, and thus outside of A048103.

For a similar reason, any term that is not a multiple of 3 may have at most 3 prime factors.

Links

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

Index entries for sequences related to primorial base.

Prog

(PARI) is_A380478 = A380477;

Crossrefs

Cf. A048103, A276086, A380459, A380474 (subsequence), A380477 (characteristic function).

Intersection of A380468 and A018252. (A380468 without primes).

Subsequence of A000469. Subsequence of A039956 (after the initial 1).

Sequence in context: A026055 A227952 A288939 * A165986 A292670 A131951

Adjacent sequences: A380475 A380476 A380477 * A380479 A380480 A380481

Keyword

nonn

Author

Antti Karttunen, Feb 03 2025

Status

approved