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

Offset

1,2

Comments

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

Links

Table of n, a(n) for n=1..9.

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

Sequence in context: A247963 A105288 A242915 * A328784 A128124 A182687

Adjacent sequences: A066681 A066682 A066683 * A066685 A066686 A066687

Keyword

nonn,hard,more

Author

Joseph L. Pe, Jan 11 2002

Extensions

a(9) from Donovan Johnson, Mar 14 2010

Status

approved