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A088465 Primes whose leftmost decimal digit is 1 and whose other decimal digits are all 7's. 1
17, 1777, 1777777777, 17777777777777, 1777777777777777777777777777777777777777777, 1777777777777777777777777777777777777777777777777777 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

In no element of this sequence can the number of 7's be congruent to 2 modulo 3.

LINKS

Table of n, a(n) for n=1..6.

Vladislav Avrutin, Prime pyramids

Makoto Kamada, Prime numbers of the form 177...77.

Index entries for primes involving repunits.

MATHEMATICA

Do[ a = 10^n + 7(10^n - 1)/9; If[ PrimeQ[a], Print[a]], {n, 1, 53}] (* Robert G. Wilson v, Dec 05 2003 *)

CROSSREFS

Cf. A002275, A089147 (number of sevens).

Sequence in context: A055414 A156675 A276808 * A001905 A221322 A135505

Adjacent sequences:  A088462 A088463 A088464 * A088466 A088467 A088468

KEYWORD

base,easy,nonn

AUTHOR

Sam Alexander, Nov 12 2003

STATUS

approved

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Last modified November 29 18:07 EST 2020. Contains 338769 sequences. (Running on oeis4.)