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 A270310 Primes ending with the same decimal digit as the previous or next prime. 4
 139, 149, 181, 191, 241, 251, 283, 293, 337, 347, 409, 419, 421, 431, 547, 557, 577, 587, 631, 641, 691, 701, 709, 719, 787, 797, 811, 821, 829, 839, 887, 907, 919, 929, 1021, 1031, 1039, 1049, 1051, 1061, 1153, 1163, 1171, 1181, 1249, 1259, 1399, 1409, 1471, 1481, 1627, 1637, 1657, 1699, 1709 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 Robert J. Lemke Oliver and Kannan Soundararajan, Unexpected biases in the distribution of consecutive primes (2016) FORMULA a(n) = prime(A270311(n)). MATHEMATICA Select[Prime@ Range@ 300, Function[k, Or[k == Mod[NextPrime@ #, 10], k == Mod[NextPrime[#, -1], 10]]]@ Mod[#, 10] &] (* Michael De Vlieger, Mar 15 2016 *) PROG (Javascript) function computeBuddyPrimes(max) {     const list = []     var prev_digit = 0     var prev_prime = 0     var curr_digit = 0     var first_friend = true     for (var n=2; n<=max; n++)     {         if (!isPrime(n)) continue;         curr_digit = n % 10         if (curr_digit === prev_digit){             // add previous prime if it was first in current group             if (first_friend) {                 list.push(prev_prime)                 first_friend = false             }             // add current prime             list.push(n)         }else{             prev_digit = curr_digit             first_friend = true         }         prev_prime = n     }     return list } function isPrime(n) {     if (n<2)         return false;     const sqrt = Math.sqrt(n)     var div = 2     while (div <= sqrt) {         if (n % div < 1)             return false;         div++     }     return true } (PARI) is(n)=isprime(n) && ((nextprime(n+1)-n)%10==0 || (n-precprime(n-1))%10==0) \\ Charles R Greathouse IV, Mar 15 2016 CROSSREFS Cf. A270311. Sequence in context: A005447 A261703 A266003 * A047652 A308788 A308796 Adjacent sequences:  A270307 A270308 A270309 * A270311 A270312 A270313 KEYWORD base,easy,nonn AUTHOR Francois Alcover, Mar 15 2016 EXTENSIONS a(15)-a(55) from Charles R Greathouse IV, Mar 15 2016 STATUS approved

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Last modified September 17 17:32 EDT 2019. Contains 327136 sequences. (Running on oeis4.)