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A032747
Super-7 Numbers (7 * n^7 contains substring '7777777' in its decimal expansion).
1
140997, 490996, 1184321, 1259609, 1409970, 1783166, 1886654, 1977538, 2457756, 2714763, 2750425, 2980991, 3043607, 3283057, 3689639, 4191601, 4258476, 4642725, 4909960, 4973029, 5242829, 5349973, 5444788, 5523544, 5682065
OFFSET
1,1
COMMENTS
The term a(6) = 1783166 is such that 7*a(6)^7 == 777777792 (mod 10^9). Therefore, all numbers congruent to a(6) (mod 5*10^8) are also in the sequence. Of course, for any term a(n), all numbers a(n)*10^k, k >= 0, are also in the sequence. - M. F. Hasler, Jul 16 2024
REFERENCES
C. A. Pickover, "Keys to Infinity", New York: Wiley, p. 7, 1995.
LINKS
Giovanni Resta, super-d numbers, personal web site "Numbers Aplenty", 2013.
Eric Weisstein's World of Mathematics, Super-d Number.
MATHEMATICA
Select[Range[6*10^6], MemberQ[Partition[IntegerDigits[7#^7], 7, 1], {7, 7, 7, 7, 7, 7, 7}]&] (* Harvey P. Dale, Sep 01 2014 *)
PROG
(PARI) is_A032747(n)=is_A014569(n, 7)
for(n=1, oo, is_A032747(n)&& print1(n", ")) \\ Quite slow, even to get the first few terms. - M. F. Hasler, Jul 16 2024
CROSSREFS
Cf. A014569 (d=3), A032743 (d=2) - A032749 (d=9).
Sequence in context: A250570 A252017 A203833 * A212373 A195438 A164527
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, May 15 1998
STATUS
approved