A212192 Triangular numbers that are the sum of exactly three distinct powers of 2.

21, 28, 276, 1540

Offset: 1

Author

Reinhard Zumkeller, May 03 2012

Keywords

• nonn

Comments

Triangular numbers with exactly three ones in their binary representation: A000120(a(n)) = 3; triangular numbers in A014311; no more terms less than A014311(1000000) = 6129982174881536975083663305496791903885182827960991744.

Crossrefs

Cf. A010054, A212190.

Programs

Haskell

a212192 n = a212192_list !! (n-1)
a212192_list = filter ((== 1) . a010054) a014311_list

Mathematica

Select[Accumulate[Range[60]],Total[IntegerDigits[#,2]]==3&] (* Harvey P. Dale, Mar 11 2023 *)