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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 Vladislav Avrutin, Prime pyramids Makoto Kamada, Prime numbers of the form 177...77. 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.)