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A069693
Triangular numbers with either no internal digits or all internal digits are 0.
8
0, 1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 300, 406, 703, 903, 3003, 4005, 8001
OFFSET
1,3
EXAMPLE
The internal digits of 3003 are "00", which are both 0. 15 has no internal digits.
MATHEMATICA
Do[ If[ Union[ Drop[ RotateLeft[ IntegerDigits[n(n + 1)/2]], -2]] == {0}, Print[n(n + 1)/2]], {n, 14, 2 10^6}]
CROSSREFS
KEYWORD
nonn,base,fini,full
AUTHOR
Amarnath Murthy, Apr 06 2002
EXTENSIONS
Corrected by Sascha Kurz, Jan 02 2003
STATUS
approved