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A123710 Indices n such that 4 = A123709(n) = number of nonzero terms in row n of triangle A123706. 3
4, 6, 8, 9, 16, 25, 27, 32, 49, 64, 81, 121, 125, 128, 169, 243, 256, 289, 343, 361, 512, 529, 625, 729, 841, 961, 1024 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Triangle A123706 is the matrix inverse of triangle A010766, where A010766(n,k) = [n/k].

Except for a(2)=6, these are proper prime powers, i.e., numbers p^k where k>1, p prime (A025475). - M. F. Hasler, Feb 12 2012

LINKS

Table of n, a(n) for n=1..27.

FORMULA

a(n) = A025475(n) for n>2 (conjectured). - M. F. Hasler, Feb 12 2012

PROG

(PARI) for(n=1, 1e4, A123709(n)==4 & print1(n", "))  \\ M. F. Hasler, Feb 12 2012

CROSSREFS

Cf. A123706, A123709, A123711, A123712; A010766.

Sequence in context: A163282 A095404 A073540 * A075243 A024370 A121719

Adjacent sequences:  A123707 A123708 A123709 * A123711 A123712 A123713

KEYWORD

nonn,more

AUTHOR

Paul D. Hanna, Oct 09 2006

STATUS

approved

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Last modified May 5 17:26 EDT 2021. Contains 343572 sequences. (Running on oeis4.)