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 A090513 Least m exceeding the previous term such that the concatenation mnm is prime. 2
 3, 7, 11, 17, 21, 23, 111, 121, 137, 183, 1003, 1031, 1047, 1081, 1103, 1131, 1153, 1249, 1253, 1273, 1277, 1301, 1317, 1321, 1323, 1333, 1343, 1371, 1387, 1439, 1463, 1467, 1469, 1473, 1549, 1589, 1617, 1621, 1727, 1763, 1779, 1787, 1791, 1867, 1883, 1901 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Michael S. Branicky, Table of n, a(n) for n = 1..231 EXAMPLE 313, 727, 11311, etc. are primes. MATHEMATICA nxt[{a_, b_}]:=Module[{m=b+2, idn=IntegerDigits[a+1]}, While[!PrimeQ[ FromDigits[ Join[IntegerDigits[m], idn, IntegerDigits[m]]]], m=m+2]; {a+1, m}]; Transpose[NestList[nxt, {1, 3}, 40]][[2]] (* Harvey P. Dale, Sep 26 2012 *) PROG (Python) from sympy import isprime from itertools import count, islice def agen(): # generator of terms m = 1 for n in count(1): while not isprime(int(str(m)+str(n)+str(m))): m += 2 yield m m += 2 print(list(islice(agen(), 46))) # Michael S. Branicky, Aug 10 2022 CROSSREFS Cf. A089749, A090514. Sequence in context: A119992 A023249 A249682 * A285600 A191050 A081515 Adjacent sequences: A090510 A090511 A090512 * A090514 A090515 A090516 KEYWORD base,nonn AUTHOR Amarnath Murthy, Dec 06 2003 EXTENSIONS More terms from Ray G. Opao, Nov 18 2004 a(36) and beyond from Michael S. Branicky, Aug 09 2022 STATUS approved

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Last modified June 22 01:41 EDT 2024. Contains 373561 sequences. (Running on oeis4.)