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A128357
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Quotients A128356(n)/Prime[n].
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8
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10, 7, 311, 127, 23, 157, 343927, 7805561, 47, 9629, 311, 25679, 821, 1470086279, 12409, 71233, 1232333, 2443783, 2939291, 71711, 352883, 181113265579, 167, 105199, 3881, 1314520253, 619, 20759, 117503, 1162660843, 1880415721, 263
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OFFSET
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1,1
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COMMENTS
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A128356(n) = {20, 21, 1555, 889, 253, 2041, 5846759, ...} = Least number k>1 (that is not the power of prime p) such that k divides (p+1)^k-1, where p = Prime[n]. Most listed terms are primes, except a(7) = 20231*17 and a(8) = 410819*19. a(15) = 12409. a(16) = 71233.
Note that all prime listed terms of a(n) coincide with terms of A128456(n) = {2,7,311,127,23,157,7563707819165039903,75368484119,47,9629,311,25679,821,...} = least prime factor of ((p+1)^p - 1)/p^2, where p = Prime[n].
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LINKS
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Table of n, a(n) for n=1..32.
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CROSSREFS
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Cf. A128356 = Least number k>1 (that is not the power of prime p) such that k divides (p+1)^k-1, where p = Prime[n]. Cf. A014960, A128360, A128358, A014960, A014956, A014951, A014949, A014946, A014945, A067945.
Cf. A128456 = least prime factor of ((p+1)^p - 1)/p^2, where p = Prime[n].
Sequence in context: A210283 A038309 A185264 * A024134 A180197 A110934
Adjacent sequences: A128354 A128355 A128356 * A128358 A128359 A128360
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KEYWORD
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hard,nonn
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AUTHOR
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Alexander Adamchuk, Mar 02 2007, Mar 09 2007
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EXTENSIONS
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Terms a(14) onwards from Max Alekseyev, Feb 08 2010
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STATUS
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approved
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