A069867 -id:A069867 - cp's OEIS frontend

A069866 Primes in which repeatedly deleting the most significant digit then the least significant digit gives a prime at every step until a single-digit prime remains.

2, 3, 5, 7, 13, 17, 23, 37, 43, 47, 53, 67, 73, 83, 97, 131, 137, 173, 179, 223, 229, 271, 331, 337, 353, 359, 373, 379, 431, 479, 523, 571, 631, 653, 659, 673, 773, 823, 829, 853, 859, 929, 937, 953, 971, 1031, 1373, 1433, 1439, 1733, 2029, 2053, 2131, 2137

Offset: 1

Amarnath Murthy, Apr 21 2002

Michael De Vlieger, Table of n, a(n) for n = 1..645 (Primes p <= 10^7).

Cf. A024770, A033664, A069867.

Select[Prime@ Range@ 400, AllTrue[FromDigits /@ Rest@ Fold[Append[#1, Delete[Last[#1], 1 - 2 Boole[EvenQ@ #2]]] &, {#}, Range[Length@ # - 1]] &@ IntegerDigits[#], PrimeQ] &] (* Michael De Vlieger, Jan 20 2018 *)

Corrected and extended by Larry Reeves (larryr(AT)acm.org), Sep 24 2002

A085414 Primes that are a concatenation of a prime and its first digit.

Original entry on oeis.org

131, 191, 313, 373, 797, 1031, 1091, 1511, 1571, 1811, 1931, 3313, 3373, 3533, 3593, 3673, 3733, 3793, 3833, 7517, 7577, 7877, 9199, 9419, 9479, 9539, 9679, 9719, 9839, 10091, 10211, 10331, 10391, 10631, 10691, 11171, 12011, 12491, 12791, 12911

Offset: 1

Zak Seidov, Jun 29 2003

Also primes remaining prime after deleting last digit, but not all such primes. See also A012833, A024770, A033664, A069867.

			13 is a term because concatenation of 13 and 1 is prime.

Cf. A085412, A085413, A012833, A024770, A033664, A069867.

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A069866 Primes in which repeatedly deleting the most significant digit then the least significant digit gives a prime at every step until a single-digit prime remains.

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A085414 Primes that are a concatenation of a prime and its first digit.

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