cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A183087 Generalized canyon primes.

Original entry on oeis.org

101, 103, 107, 109, 307, 313, 317, 401, 409, 419, 439, 503, 509, 523, 547, 601, 607, 613, 617, 619, 647, 659, 701, 709, 719, 727, 739, 757, 769, 809, 823, 827, 829, 839, 857, 859, 907, 919, 929, 937, 947, 967, 1013, 1019, 1039, 1049, 1069, 2017, 2027, 2029
Offset: 1

Views

Author

Omar E. Pol, Jan 19 2011

Keywords

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

Examples

			Illustration of 751379 as a generalized canyon prime:
. . . . . 9
. . . . . .
7 . . . 7 .
. . . . . .
. 5 . . . .
. . . . . .
. . . 3 . .
. . . . . .
. . 1 . . .
. . . . . .
		

Crossrefs

Programs

  • 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

Formula

A000040 INTERSECT A183086.

Extensions

Missing 601 inserted by Michael S. Branicky, Aug 04 2022