A356398 a(1) = 4, and for any n > 1, a(n+1) is the a(n)-th squarefree number.

4, 5, 6, 7, 10, 14, 21, 33, 53, 85, 138, 222, 366, 599, 985, 1613, 2651, 4357, 7169, 11795, 19401, 31913, 52487, 86347, 142021, 233615, 384277, 632091, 1039741, 1710305, 2813358, 4627790, 7612435, 12521926, 20597674, 33881799, 55733298, 91677666, 150803687

Offset

1,1

Comments

See A071255 for a similar sequence.

The ratio a(n+1)/a(n) tends to Pi^2/6 (A013661) as n tends to infinity.

Links

Table of n, a(n) for n=1..39.

Rémy Sigrist, C program

Formula

a(n+1) = A005117(a(n)).

Example

a(1) = 4 and the fourth squarefree number is 5, so a(2) = 5.

Prog

(C) See Links section.

Crossrefs

Cf. A005117, A006508, A007097, A013661, A071255.

Sequence in context: A080723 A288737 A139448 * A364803 A022561 A213524

Adjacent sequences: A356395 A356396 A356397 * A356399 A356400 A356401

Keyword

nonn

Author

Rémy Sigrist, Aug 05 2022

Status

approved