A066684 - OEIS

A066684

Numbers k such that prime(k) is congruent to sigma(k) (mod k), where prime(n) denotes the n-th prime.

1, 2, 4, 5, 181, 324, 1253, 252649, 69789901

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OFFSET

1,2

COMMENTS

a(10) > 10^12. - Donovan Johnson, Mar 14 2010

LINKS

EXAMPLE

prime(5) = 11 is congruent to sigma(5) = 6 (mod 5), so 5 is in the sequence.

MATHEMATICA

Select[ Range[ 1, 10^5 ], Mod[ DivisorSigma[ 1, # ], # ] == Mod[ Prime[ # ], # ] & ]

CROSSREFS

KEYWORD

nonn,hard,more

AUTHOR

Joseph L. Pe, Jan 11 2002

EXTENSIONS

a(9) from Donovan Johnson, Mar 14 2010

STATUS

approved