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Product of digits + 1 is prime, sum of digits + 1 is prime and sum of digits - 1 is prime.
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%I #16 Dec 05 2024 17:59:52

%S 4,6,22,66,112,114,121,123,129,132,141,147,156,165,174,189,192,198,

%T 211,213,219,231,237,273,279,291,297,312,321,327,345,354,369,372,396,

%U 411,417,435,453,459,468,471,477,486,495,516,534,543,549,561,567,576,594

%N Product of digits + 1 is prime, sum of digits + 1 is prime and sum of digits - 1 is prime.

%H Harry J. Smith, <a href="/A061595/b061595.txt">Table of n, a(n) for n = 1..1003</a>

%e For 147 we have (1*4*7) + 1 = 29, (1+4+7) + 1 = 13, (1+4+7) - 1 = 11.

%p a := proc (n) local nn: nn := convert(n, base, 10): if isprime(1+product(nn[j], j = 1 .. nops(nn))) = true and isprime(1+sum(nn[j], j = 1 .. nops(nn))) = true and isprime(-1+sum(nn[j], j = 1 .. nops(nn))) = true then n else end if end proc: seq(a(n), n = 1 .. 615); # _Emeric Deutsch_, Aug 02 2009

%o (PARI) isok(k)={my(d=digits(k), s=vecsum(d)); isprime(s+1) && isprime(s-1) && isprime(vecprod(d)+1)} \\ _Harry J. Smith_, Jul 25 2009

%Y Subsequence of A167711.

%K nonn,base

%O 1,1

%A _Felice Russo_, May 22 2001

%E a(1)=4 and a(2)=6 added by _Emeric Deutsch_, Aug 02 2009