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 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 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

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