A086073 Number of 2's in decimal expansion of triangular number n(n+1)/2.

0, 0, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 2, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 2, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0

Offset: 0

Author

Jason Earls, Jul 08 2003

Keywords

• base
• nonn

Examples

			tri(49)=1225, so a(49)=2 and tri(651)=212226, so a(651)=4.
		

Crossrefs

Cf. 0's A086071, 1's A086072, 3's A086074, 4's A086075, 5's A086076, 6's A086077, 7's A086078, 8's A086079, 9's A086080.

Programs

Mathematica

DigitCount[#,10,2]&/@Accumulate[Range[0,120]] (* Harvey P. Dale, Jan 02 2016 *)