A117978 - OEIS

A117978

Triangular numbers with only even digits.

0, 6, 28, 66, 406, 666, 820, 2080, 2628, 8646, 28680, 42486, 48828, 64620, 66066, 80200, 84666, 200028, 204480, 228826, 264628, 288420, 426426, 446040, 468028, 484620, 600060, 626640, 644680, 686206, 828828, 886446, 2222886, 2248260, 2862028, 2888406

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OFFSET

1,2

COMMENTS

There are infinitely many terms. For example all 88...88 6 44...44 6 with an equal number of 8's and 4's (their triangular indices being A185127). - Shyam Sunder Gupta, Aug 16 2025

LINKS

Jon E. Schoenfield, Table of n, a(n) for n = 1..10000 (first 1000 terms from Harvey P. Dale)

Shyam Sunder Gupta, Triangular Numbers, Exploring the Beauty of Fascinating Numbers, Springer (2025) Ch. 3, 82-125.

MATHEMATICA

Select[Accumulate[Range[0, 5000]], Count[IntegerDigits[#], _?(OddQ)] ==0&] (* Harvey P. Dale, Oct 21 2011 *)

CROSSREFS

Intersection of A000217 and A014263.

Cf. A117960, A185127.

Sequence in context: A014635 A227970 A034955 * A119174 A326134 A343512

Adjacent sequences: A117975 A117976 A117977 * A117979 A117980 A117981

KEYWORD

base,nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), May 03 2006

EXTENSIONS

Corrected (a(32) was in error) and extended by Harvey P. Dale, Oct 21 2011

STATUS

approved