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 A134971 Canyon primes. 9
 101, 313, 727, 757, 919, 929, 3023, 3203, 7027, 7057, 7127, 7207, 7237, 7247, 7307, 7417, 7457, 7507, 7517, 7537, 7547, 7607, 9029, 9049, 9059, 9109, 9209, 9239, 9319, 9349, 9419, 9439, 9479, 9539, 9619, 9629, 9649, 9679, 9689, 9719, 9739, 9749, 9769, 9829 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Intersection of prime numbers and Canyon numbers ("Canyon primes"). This sequence is finite because A134970 is. There are 9237 Canyon primes (compare to 116505 Canyon numbers total). The largest Canyon prime (and last element of this sequence) is a(9237) = 98765432101456789. LINKS Kellen Myers, Table of n, a(n) for n = 1..9237 FORMULA A000040 INTERSECT A134970. EXAMPLE Illustration of 751367 as a Canyon prime: . . . . . . . . . . . . 7 . . . . 7 . . . . 6 . . 5 . . . . . . . . . . . . . 3 . . . . . . . . . . 1 . . . . . . . . . MATHEMATICA S = {}; c = 1; For[n = 1, n <= 9, n++, L = 2 n - 1; d = Join[Reverse[Range[1, n - 1]], Range[0, n - 1]]; If[Mod[n, 2] != 0 && n != 5, For[j = 1, j < 2^L, j++, Dig = d[[Map[#[[1]] &, Position[IntegerDigits[j, 2, L], 1]]]]; min = Min[Dig]; If[Length[Position[Dig, min]] == 1, p = FromDigits[Join[{n}, Dig, {n}]]; If[PrimeQ[p], S = Append[S, p]]; ]; ]; ]; ]; (* Kellen Myers, Jan 18 2011 *) PROG (Python) from sympy import isprime from itertools import chain, combinations as combs ups = list(chain.from_iterable(combs(range(10), r) for r in range(2, 11))) s = set(L[::-1] + R[1:] for L in ups for R in ups if L[0] == R[0]) afull = sorted(filter(isprime, (int("".join(map(str, t))) for t in s if t[0] == t[-1]))) print(afull[:44]) # Michael S. Branicky, Jan 16 2023 CROSSREFS Cf. A000040, A134951, Primes in A134970. Sequence in context: A256048 A252942 A090287 * A082770 A161907 A195855 Adjacent sequences: A134968 A134969 A134970 * A134972 A134973 A134974 KEYWORD nonn,base,fini,full AUTHOR Omar E. Pol, Nov 25 2007 EXTENSIONS All terms past 3203, more comments, etc. by Kellen Myers, Jan 18 2011 STATUS approved

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Last modified April 1 09:24 EDT 2023. Contains 361688 sequences. (Running on oeis4.)