A275658 Lexicographically earliest increasing sequence such that the a(n)th term of the sequence has n divisors.

1, 2, 4, 9, 10, 11, 12, 13, 14, 16, 18, 64, 66, 100, 101, 112, 113, 1024, 1025, 1026, 1027, 1028, 1029, 1030, 1031, 1032, 1033, 1034, 1035, 1036, 1037, 1038, 1039, 1040, 1041, 1042, 1043, 1044, 1045, 1046, 1047, 1048, 1049, 1050, 1051, 1052, 1053, 1054, 1055

Offset

1,2

Links

Jaroslav Krizek, Table of n, a(n) for n = 1..1000

Formula

A000005(a(a(n))) = tau(a(a(n))) = n.

Example

a(1)=1 because tau(1)=1; a(2)=2 because tau(2)=2; a(3) cannot be 3 because tau(3)=2, a(3)=4 (4 is the smallest number x>3); if a(3)=4, a(4) must be the smallest number x>a(3) with 3 divisors, a(4)=9; a(9) must be number with 4 divisors and must keep increase of the sequence, a(9)=14; a(5)=10 because 10>a(4); a(6)=11; a(7)=12; a(8)=13; etc...

Crossrefs

Cf. A000005.

Sequence in context: A076661 A258710 A246515 * A267414 A072583 A178488

Adjacent sequences: A275655 A275656 A275657 * A275659 A275660 A275661

Keyword

nonn

Author

Jaroslav Krizek, Aug 04 2016

Status

approved