A054481 Highest common factor of successive highly composite numbers (1), A002182.

1, 2, 2, 6, 12, 12, 12, 12, 60, 60, 60, 120, 360, 120, 420, 420, 840, 2520, 2520, 2520, 5040, 5040, 5040, 2520, 2520, 5040, 5040, 27720, 27720, 55440, 55440, 55440, 55440, 166320, 55440, 110880, 55440, 360360, 360360

Offset

2,2

Comments

Not the same as the first differences of A002182. The latter are given by A262501, which differs from this sequence for the first time at n=25, where A262501(25) = 17640, while here the 25th term a(26) is 2520. The sequences differ next time at positions n = 52, 53, 54, 64, 67, 82, 83, 84, 85, 86, 87, 88, 90, 91, 96, 100, 106, ... (when one-based indexing as in A262501 is used). - Antti Karttunen, Sep 24 2015

Links

Antti Karttunen, Table of n, a(n) for n = 2..1000 (computed from the b-file of A002182 provided by T. D. Noe)

Formula

a(n) = GCD(A002182(n-1), A002182(n)) = A002182(n)/A054483(n) = A002182(n-1)/A054482(n).

Example

a(7)=12 because A002182(7)=36, A002182(6)=24 and GCD(36,24)=12.

Crossrefs

Cf. A002182, A054482, A054483, A262501.

Sequence in context: A285529 A305215 A219694 * A262501 A225422 A290518

Adjacent sequences: A054478 A054479 A054480 * A054482 A054483 A054484

Keyword

easy,nonn

Author

Henry Bottomley, Mar 31 2000

Extensions

Erroneous comment (wrong interpretation) removed by Antti Karttunen, Sep 25 2015

Status

approved