A182237 Numbers occurring exactly in 2 rows of Pascal's triangle.

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

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 * A337612 A315250 A315251

Adjacent sequences: A182234 A182235 A182236 * A182238 A182239 A182240

Keyword

nonn

Author

Reinhard Zumkeller, Dec 24 2012

Status

approved