A328586 Even numbers n for which A257993(n) is equal to A257993(A276086(A276086(n))), where A276086 converts the primorial base expansion of n into its prime product form, and A257993 returns the index of the least prime not present in its argument.

6, 18, 36, 48, 66, 78, 96, 108, 126, 138, 156, 168, 186, 198, 222, 234, 252, 264, 282, 294, 312, 324, 342, 354, 372, 384, 402, 414, 426, 438, 456, 468, 486, 498, 516, 528, 546, 558, 576, 588, 606, 618, 642, 654, 672, 684, 702, 714, 732, 744, 762, 774, 792, 804, 822, 834, 846, 858, 876, 888, 906, 918, 936, 948, 966, 978, 996, 1008

Offset

1,1

Comments

All terms are multiples of 6, but very few multiples of 5 (and thus of 10) are present: the first ones are at a(169) = 2520 and a(254) = 3780. Among the first 10000 terms, there are only 28 ending with decimal digit 0, while those that end with either 2 or 4 are 2450 both, and with either 6 or 8, both have 2536 each.

Other multiples of six are in A328587 and A328589.

Links

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

Index entries for sequences related to primorial base

Prog

(PARI)
A257993(n) = { for(i=1, oo, if(n%prime(i), return(i))); }
A276086(n) = { my(m=1, p=2); while(n, m *= (p^(n%p)); n = n\p; p = nextprime(1+p)); (m); };
A328578(n) = A257993(A276086(A276086(n)));
isA328586(n) = ((!(n%2))&&(A328578(n) == A257993(n)));

Crossrefs

Cf. A257993, A276086, A328578, A328316, A328317, A328633.

Even terms in A328585. Cf. also A328587, A328588, A328589.

Sequence in context: A111147 A333821 A358843 * A172522 A152539 A069958

Adjacent sequences: A328583 A328584 A328585 * A328587 A328588 A328589

Keyword

nonn

Author

Antti Karttunen, Oct 21 2019

Status

approved