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A182237 Numbers occurring exactly in 2 rows of Pascal's triangle. 6
6, 10, 15, 20, 21, 28, 35, 36, 45, 55, 56, 66, 70, 78, 84, 91, 105, 126, 136, 153, 165, 171, 190, 220, 231, 252, 253, 276, 286, 300, 325, 330, 351, 364, 378, 406, 435, 455, 462, 465, 495, 496, 528, 560, 561, 595, 630, 666, 680, 703, 715, 741, 780, 792, 816 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A059233(a(n)) = 2.

LINKS

Reinhard Zumkeller and T. D. Noe, Table of n, a(n) for n = 1..1000 (first 100 terms from Reinhard Zumkeller)

Wikipedia, Singmaster's conjecture

Index entries for triangles and arrays related to Pascal's triangle

MATHEMATICA

nn = 1000; t = Table[s = {}; k = 1; While[k++; b = Binomial[n, k]; k <= n/2 && b <= nn, AppendTo[s, b]]; s, {n, nn}]; t2 = Select[t, Length[#] > 0 &]; Transpose[Select[Tally[Sort[Flatten[t2]]], #[[2]] == 1 &]][[1]] (* T. D. Noe, Mar 13 2013 *)

PROG

(Haskell)

import Data.List (elemIndices)

a182237 n = a182237_list !! (n-1)

a182237_list = map (+ 2 ) $ elemIndices 2 a059233_list

CROSSREFS

Cf. A098565.

Sequence in context: A315249 A319382 A006987 * A315250 A315251 A315252

Adjacent sequences:  A182234 A182235 A182236 * A182238 A182239 A182240

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Dec 24 2012

STATUS

approved

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Last modified November 20 02:34 EST 2019. Contains 329323 sequences. (Running on oeis4.)