A381372 -id:A381372 - cp's OEIS frontend

A381510 Smaller of two consecutive primes p and q, both ending with 7, such that q - p = 10n, or -1 if no such primes exist.

337, 887, 4297, 33247, 31907, 124367, 218287, 1122287, 1964987, 1313467, 1468277, 7160227, 5518687, 16525757, 13626257, 71880637, 27915737, 17051707, 394059907, 566348087, 252314747, 472865287, 1289694257, 633418787, 1588640437, 944192807, 1391048047, 7059848287

Offset: 1

Jean-Marc Rebert, Feb 25 2025

			a(1) = 337, because 337 and 337 + 10 = 347 are two consecutive primes with the same last digit 7 and no smaller prime has this property.

Cf. A101232, A140791, A380785, A381372.

a(n) = my(p=7); while (!isprime(p) || ((nextprime(p+1)-p) != 10*n), p+=10); p; \\ Michel Marcus, Feb 25 2025

from sympy import nextprime, isprime
def A381510(n):
    p = 17
    while (q:=nextprime(p)):
        if q-p == 10*n:
            return p
        p = q+9-(q+2)%10
        while not isprime(p):
            p += 10 # Chai Wah Wu, Mar 09 2025

A381511 Smaller of two consecutive primes p and q, both ending with 9, such that q - p = 10*n, or -1 if no such primes exist.

Original entry on oeis.org

139, 3089, 5749, 20809, 60539, 110359, 173359, 618719, 1294849, 838249, 6877109, 1895359, 11188759, 7621259, 35560009, 33803689, 124956059, 92801029, 142414669, 378043979, 229316459, 390932389, 1095750599, 995151679, 2174082649, 2603726969, 3402493709, 1997191249

Offset: 1

Jean-Marc Rebert, Feb 25 2025

			a(1) = 139, because 139 and 139 + 10 = 149 are two consecutive primes with the same last digit 9 and no smaller p has this property.

Cf. A101232, A140791, A380785, A381372. A381510.

a(n) = my(p=9); while (!isprime(p) || ((nextprime(p+1)-p) != 10*n), p+=10); p; \\ Michel Marcus, Feb 25 2025

from sympy import isprime, nextprime
def A381511(n):
    p = 19
    while (q:=nextprime(p)):
        if q-p == 10*n:
            return p
        p = q+9-(q%10)
        while not isprime(p):
            p += 10 # Chai Wah Wu, Mar 08 2025

cp's OEIS Frontend

A381510 Smaller of two consecutive primes p and q, both ending with 7, such that q - p = 10n, or -1 if no such primes exist.

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