OFFSET
1,1
COMMENTS
Primes in A183086. Supersequence of A134971 because the restriction that both cliffs are at same level (first digit equal to the final digit) is dropped here.
This sequence is finite because A183086 is.
Questions: How many terms are there in this sequence?
What is the largest term?
There are 24356 terms, the largest of which is 98765432101456789. - Michael S. Branicky, Aug 04 2022
LINKS
Michael S. Branicky, Table of n, a(n) for n = 1..24356 (full sequence)
EXAMPLE
Illustration of 751379 as a generalized canyon prime:
. . . . . 9
. . . . . .
7 . . . 7 .
. . . . . .
. 5 . . . .
. . . . . .
. . . 3 . .
. . . . . .
. . 1 . . .
. . . . . .
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)))
print(afull[:50]) # Michael S. Branicky, Aug 04 2022
CROSSREFS
KEYWORD
nonn,base,fini,full
AUTHOR
Omar E. Pol, Jan 19 2011
EXTENSIONS
Missing 601 inserted by Michael S. Branicky, Aug 04 2022
STATUS
approved