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%I #7 Jul 28 2022 03:31:59
%S 1,2,4,5,181,324,1253,252649,69789901
%N Numbers k such that prime(k) is congruent to sigma(k) (mod k), where prime(n) denotes the n-th prime.
%C a(10) > 10^12. - _Donovan Johnson_, Mar 14 2010
%e prime(5) = 11 is congruent to sigma(5) = 6 (mod 5), so 5 is in the sequence.
%t Select[ Range[ 1, 10^5 ], Mod[ DivisorSigma[ 1, # ], # ] == Mod[ Prime[ # ], # ] & ]
%K nonn,hard,more
%O 1,2
%A _Joseph L. Pe_, Jan 11 2002
%E a(9) from _Donovan Johnson_, Mar 14 2010
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