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%I #13 Nov 29 2020 02:09:23
%S 1,15,35,63,95,143,161,215,255,287,323,485,511,575,767,1023,1295,1457,
%T 1535,1727,1943,2047,2303,2915,3071,3455,3887,4095,4607,5183,5831,
%U 7775,9215,10367,11663,12287,13823,16383,17495,18431,20735,24575,26243,31103,32767
%N Nonprime solutions to k == -1 (mod phi(k+1)).
%C Odd terms in A005105 are primes solutions to p==-1 (mod phi(p+1)).
%H Amiram Eldar, <a href="/A067930/b067930.txt">Table of n, a(n) for n = 1..336</a> (terms below 5*10^10)
%t Select[Range[30000], !PrimeQ[#] && Divisible[# + 1, EulerPhi[# + 1]] &] (* _Amiram Eldar_, Nov 29 2020 *)
%o (PARI) isok(m) = !isprime(m) && (Mod(m, eulerphi(m+1)) == -1); \\ _Michel Marcus_, Nov 29 2020
%Y Cf. A000010, A005105.
%K nonn
%O 1,2
%A _Benoit Cloitre_, Feb 22 2002
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