login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A086073 Number of 2's in decimal expansion of triangular number n(n+1)/2. 9
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 23 08:57 EDT 2019. Contains 328345 sequences. (Running on oeis4.)