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A130202 Odious triangular numbers. 2

%I

%S 1,21,28,55,91,171,253,276,351,406,465,496,595,666,820,861,1081,1225,

%T 1378,1431,1485,1540,1653,1770,1891,2211,2346,2485,2850,3003,3160,

%U 3240,3403,3655,3916,4186,4371,4560,4753,4950

%N Odious triangular numbers.

%H Harvey P. Dale, <a href="/A130202/b130202.txt">Table of n, a(n) for n = 0..1000</a>

%F a(n) = A130201(n)/2. Multiplication by 2 preserves odiousness, hence this sequence is odious oblong numbers divided by 2.

%t Select[Table[n(n + 1)/2, {n, 100}], OddQ[Plus @@ IntegerDigits[ #, 2]] &]

%t Select[Accumulate[Range[100]],OddQ[DigitCount[#,2,1]]&] (* _Harvey P. Dale_, Dec 04 2016 *)

%Y Cf. This sequence is the intersection of odious (A000069) and triangular (A000217) numbers.

%K nonn

%O 0,2

%A _Tanya Khovanova_, May 16 2007

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Last modified September 25 19:48 EDT 2017. Contains 292500 sequences.