A130202 - OEIS

%I #10 Dec 09 2019 09:21:26

%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 Amiram Eldar, <a href="/A130202/b130202.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harvey P. Dale)

%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 1,2

%A _Tanya Khovanova_, May 16 2007

%E Offset corrected by _Amiram Eldar_, Dec 09 2019