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Sum of p = prime(n) and largest prime divisor of p-1.
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%I #19 May 11 2024 20:24:25

%S 5,7,10,16,16,19,22,34,36,36,40,46,50,70,66,88,66,78,78,76,92,124,100,

%T 100,106,120,160,112,120,134,144,154,162,186,156,170,166,250,216,268,

%U 186,210,196,204,210,218,260,340,248,262,256,246,256,259,394,336,276,300

%N Sum of p = prime(n) and largest prime divisor of p-1.

%F a(n) = p + A006530(p-1) where p = prime(n).

%e a(2) = prime(2) + gpf(prime(2) - 1) = 3 + gpf(2) = 3 + 2 = 5.

%o (PARI) cminuspm2(n) = \\ prime + maxprime of prime-1

%o { forprime(x=5,n, forstep(p=x,2,-1, if(isprime(p) & (x-1)%p==0,print1(x+p,","); break); ) ) }

%o (PARI) a(n) = my(p=prime(n)); p+vecmax(factor(p-1)[,1]); \\ _Michel Marcus_, May 07 2024

%Y Cf. A006530, A023503, A274022.

%K easy,nonn

%O 2,1

%A _Cino Hilliard_, Aug 12 2003

%E Offset 2 and a(2) from _Michel Marcus_, May 07 2024

%E Edited by _Jon E. Schoenfield_, May 07 2024