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A078494 Primes occurring only once in their decade. 23

%I #15 Sep 08 2022 08:45:08

%S 97,113,127,149,181,211,241,293,307,367,397,419,421,457,479,487,557,

%T 587,631,661,683,691,719,727,743,773,787,797,809,811,839,863,877,907,

%U 929,937,953,967,983,1009,1021,1049,1051,1087,1117,1163,1171,1193,1201,1249

%N Primes occurring only once in their decade.

%H Alois P. Heinz, <a href="/A078494/b078494.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) ~ n log n. In particular, most primes are in this sequence. - _Charles R Greathouse IV_, Sep 07 2012

%o (PARI) decade1pr(n1,n2) = { forstep(x=n1,n2,10, if(isprime(x+1) && !isprime(x+3) && !isprime(x+7) && !isprime(x+9), print1(x+1" ");); if(isprime(x+3) && !isprime(x+1) && !isprime(x+7) && !isprime(x+9), print1(x+3" ");); if(isprime(x+7) && !isprime(x+1) && !isprime(x+3) && !isprime(x+9), print1(x+7" ");); if(isprime(x+9) && !isprime(x+1) && !isprime(x+3) && !isprime(x+7), print1(x+9" ");); ); }

%o (Magma) &cat [PrimesInInterval(10*n+1, 10*n+9): n in [0..150] | IsOne(#PrimesInInterval(10*n+1, 10*n+9))]; // _Bruno Berselli_, Sep 05 2012

%Y Cf. A078500.

%K nonn,easy,base

%O 1,1

%A _Cino Hilliard_, Jan 04 2003

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)