OFFSET
1,2
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..10000
EXAMPLE
1830 is a term as 1, 8, 3 and 0 have odd and even parity alternately.
MATHEMATICA
altQ[n_] := n < 10 || Union[ Total /@ Partition[ Mod[ IntegerDigits@n, 2], 2, 1]] == {1}; t[n_] := n (n + 1)/2; Select[ t@ Range@ 400, altQ] (* Giovanni Resta, Aug 17 2018 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Amarnath Murthy, Mar 19 2002
EXTENSIONS
More terms from Sascha Kurz, Mar 23 2002
STATUS
approved