A086072 Number of 1's in decimal expansion of triangular number n(n+1)/2.

0, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 1, 1, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 1, 2, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 3, 1, 1, 2, 1, 1, 0, 1, 2, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 2, 0, 0, 0

Offset

0,19

Links

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

Example

tri(6)=21, so a(6)=1 and tri(1541)=1188111, so a(1541)=5.

Mathematica

Table[DigitCount[(n(n+1))/2, 10, 1], {n, 0, 110}] (* Harvey P. Dale, Apr 24 2011 *)
DigitCount[#, 10, 1]&/@Accumulate[Range[0, 110]] (* Harvey P. Dale, Jun 25 2014 *)

Crossrefs

Cf. 0's A086071, 2's A086073, 3's A086074, 4's A086075, 5's A086076, 6's A086077, 7's A086078, 8's A086079, 9's A086080.

Sequence in context: A321144 A309048 A379666 * A086009 A086010 A321929

Adjacent sequences: A086069 A086070 A086071 * A086073 A086074 A086075

Keyword

base,nonn

Author

Jason Earls, Jul 08 2003

Status

approved