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A119586 Triangle where a(n,m) = (n+1-m)th positive integer with (m+1) divisors. 2
2, 3, 4, 5, 9, 6, 7, 25, 8, 16, 11, 49, 10, 81, 12, 13, 121, 14, 625, 18, 64, 17, 169, 15, 2401, 20, 729, 24, 19, 289, 21, 14641, 28, 15625, 30, 36, 23, 361, 22, 28561, 32, 117649, 40, 100, 48, 29, 529, 26, 83521, 44, 1771561, 42, 196, 80, 1024, 31, 841, 27 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..58.

EXAMPLE

Looking at the 4th row, 7 is the 4th positive integer with 2 divisors, 25 is the 3rd positive integer with 3 divisors, 8 is the 2nd positive integer with 4 divisors and 16 is the first positive integer with 5 divisors. So the 4th row is (7,25,8,16).

MATHEMATICA

t[n_, m_] := Block[{c = 0, k = 1}, While[c < n + 1 - m, k++; If[DivisorSigma[0, k] == m + 1, c++ ]]; k]; Table[ t[n, m], {n, 11}, {m, n}] // Flatten (* Robert G. Wilson v *)

CROSSREFS

k-th Column: A000040, A001248, A007422, A030514, A030515, A030516, A030626, A030627, A030628, A030629, A030630, A030631, A030632, A030633, A030634, A030635, A030636, A030637, A030638.

Cf. A073915. Main diagonal: A005179.

Sequence in context: A171100 A240062 A255129 * A095904 A096153 A083140

Adjacent sequences:  A119583 A119584 A119585 * A119587 A119588 A119589

KEYWORD

nonn,tabl

AUTHOR

Leroy Quet, May 31 2006

EXTENSIONS

More terms from Robert G. Wilson v, Jun 07 2006

STATUS

approved

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Last modified April 19 18:58 EDT 2019. Contains 322290 sequences. (Running on oeis4.)