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%I #13 Aug 09 2014 23:02:53
%S 211,257,269,461,463,467,523,547,769,829,839,947,967,983,1129,1213,
%T 1259,1327,1361,1381,1429,1433,1453,1487,1619,1667,1721,1723,1741,
%U 1811,1847,2143,2153,2161,2243,2251,2311,2339,2357,2371,2473,2531,2591,2593,2617,2659
%N Primes p such that p +/- product_of_digits(p) are both semiprimes.
%H K. D. Bajpai, <a href="/A240918/b240918.txt">Table of n, a(n) for n = 1..10460</a>
%e 211 is in the sequence because it is prime, and because 211 + (2 * 1 * 1) = 213 = 3 * 71 and 211 - (2 * 1 * 1) = 209 = 11 * 19 both are semiprimes.
%e 461 is in the sequence because it is prime, and because 461 + (4 * 6 * 1) = 485 = 5 * 97 and 461 - (4 * 6 * 1) = 437 = 19 * 23 both are semiprimes.
%t Select[Prime[Range[500]], PrimeOmega[(Times @@ IntegerDigits[#] + #)] == 2 && PrimeOmega[(Times @@ IntegerDigits[#] - #)] == 2 &]
%o (PARI)
%o forprime(p=10,10^4,d=digits(p);pp=prod(i=1,#d,d[i]);if(bigomega(p+pp)==2&&bigomega(p-pp)==2,print1(p,", "))) \\ _Derek Orr_, Aug 02 2014
%Y Cf. A000040, A001358, A227217.
%K nonn,base,less
%O 1,1
%A _K. D. Bajpai_, Aug 02 2014
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