A119765 Irregular array where row n is the positive integers which divide the number of terms in all previous rows. a(1)=1.

1, 1, 1, 2, 1, 2, 4, 1, 7, 1, 3, 9, 1, 2, 3, 4, 6, 12, 1, 2, 3, 6, 9, 18, 1, 2, 3, 4, 6, 8, 12, 24, 1, 2, 4, 8, 16, 32, 1, 2, 19, 38, 1, 2, 3, 6, 7, 14, 21, 42, 1, 2, 5, 10, 25, 50, 1, 2, 4, 7, 8, 14, 28, 56, 1, 2, 4, 8, 16, 32, 64, 1, 71, 1, 73, 1, 3, 5, 15, 25, 75, 1, 3, 9, 27, 81, 1, 2, 43, 86

Offset

1,4

Links

Table of n, a(n) for n=1..90.

Example

Array begins:
1
1
1,2
1,2,4
1,7
1,3,9
12 terms make up these 6 rows. So row 7 is the divisors of 12, (1,2,3,4,6,12).

Maple

A119765 := proc(nmax) local a, dvs; a := [1] ; while nops(a) < nmax do dvs := numtheory[divisors](nops(a)) ; a := [op(a), op(dvs) ] ; od ; end: a := A119765(300) ; for i from 1 to nops(a) do printf("%d, ", a[i]) ; od ; # R. J. Mathar, Jun 23 2006

Prog

(PLT Scheme) ;; positive-divisors gives the list of divisors of n in decreasing order
(define (A119765 n seq)
(cond
[(= n 0) seq]
[else (A119765 (sub1 n) (append seq (reverse (positive-divisors (length seq)))))]))
(A119765 30 (list 1)) ;; Joshua Zucker, Jun 21 2006

Crossrefs

Sequence in context: A244419 A157751 A177701 * A303325 A077901 A105619

Adjacent sequences: A119762 A119763 A119764 * A119766 A119767 A119768

Keyword

nonn,tabf

Author

Leroy Quet, Jun 18 2006

Extensions

More terms from Joshua Zucker and R. J. Mathar, Jun 21 2006

Status

approved