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A079654 Triangular numbers using only the straight digits 1, 4 and 7. 2
1, 171, 741, 1711, 117144471, 417417171, 7417744447141, 177141144447177414711441, 1417711714147441711474771771 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Probably finite.

LINKS

Table of n, a(n) for n=1..9.

G. Resta, Tridigital Triangular Numbers

MATHEMATICA

Do[ If[ Union[ Join[ IntegerDigits[n(n + 1)/2], {1, 4, 7}]] == {1, 4, 7}, Print[n(n + 1)/2]], {n, 0, 3*10^7}]

CROSSREFS

Cf. A000217, A028373, A053899, A119127. See A119033 for a table of cross-references.

Sequence in context: A043407 A031691 A158220 * A220869 A251329 A221754

Adjacent sequences:  A079651 A079652 A079653 * A079655 A079656 A079657

KEYWORD

base,nonn

AUTHOR

Shyam Sunder Gupta, Jan 23 2003

EXTENSIONS

Edited and extended by Robert G. Wilson v, Jan 24 2003

More terms from Giovanni Resta, May 10 2006

STATUS

approved

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Last modified January 19 04:18 EST 2021. Contains 340262 sequences. (Running on oeis4.)