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

0,50

Links

Table of n, a(n) for n=0..104.

Example

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

Mathematica

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

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.

Sequence in context: A261160 A270668 A196272 * A053622 A016408 A316868

Adjacent sequences: A086070 A086071 A086072 * A086074 A086075 A086076

Keyword

base,nonn

Author

Jason Earls, Jul 08 2003

Status

approved