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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 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.)