A127889 -id:A127889 - cp's OEIS frontend

A088603 a(n) = smallest prime in which n substrings containing the most significant digit are primes.

2, 23, 233, 2333, 23333, 233993, 2339933, 23399339, 1979339333, 23339531339, 293999994791, 3733799959397, 233323747999733, 2333939994739931, 23833939369399333, 238339393693993337, 23833939369399333613

Offset: 1

Amarnath Murthy, Oct 15 2003

Agrees with A127889 for 8 terms, but A127889 ends there while this sequence continues. - Ray Chandler, Mar 13 2007

Cf. A088604, A127889.

f(n, d, spare) = local(p, r); if (!d, return(n)); for (i = 0, 9, p = 10*n + i; if (isprime(p) || spare, r = f(p, d - 1, spare - 1 + isprime(p))); if (r, return(r))); 0;
a(n) = local(i, r); i = 0; while (1, r = f(0, n + i, i); if (r, return(r), i++)); \\ David Wasserman, Aug 12 2005

Corrected and extended by David Wasserman, Aug 12 2005

A127890 Largest n-digit right-truncatable prime.

Original entry on oeis.org

7, 79, 797, 7393, 73939, 739399, 7393933, 73939133

Offset: 1

Ray Chandler, Feb 04 2007

For a variant see the Howard reference. - Alexander R. Povolotsky, Dec 23 2007

Right-truncatable means that the integer part of successive divisions by 10 always yields primes (or zero). - M. F. Hasler, Nov 07 2018

Toby Howard, "Magic Pi - The Magic of Numbers", PC Advisor magazine, May 1998.

I. O. Angell and H. J. Godwin, On Truncatable Primes, Math. Comput. 31, 265-267, 1977.
Jens Fehlau, 73939133 - Probably the Most Interesting Prime Number [Part 1] and [Part 2], Flammable Maths videos (2020).
Index entries for sequences related to truncatable primes

Cf. A024770, A050986, A127889.

A127890=vector(8, n, p=concat(apply(t->primes([t, t+1]*10), if(n>1, p)));p[#p]) \\ M. F. Hasler, Nov 07 2018

A100893 a(n) = smallest n-digit prime formed by appending a digit to a(n-1); a(1) = 2.

Original entry on oeis.org

2, 23, 233, 2333, 23333

Offset: 1

Jorge Coveiro, Jan 10 2005

This sequence is finite because there is no prime a(6) since 233331,233333,233337,233339 are not prime.

This is an initial subsequence of A048549, A065122, A088603, and A127889; and for any b, the base b analog of this sequence is an initial subsequence of the base b analog of each of these three sequences. [From Franklin T. Adams-Watters, Jun 27 2009]

			a(1)=2
a(2)=23
a(3)=233
a(4)=2333
a(5)=23333

cp's OEIS Frontend

A088603 a(n) = smallest prime in which n substrings containing the most significant digit are primes.

Views

Author

Keywords

Comments

Crossrefs

Programs

PARI

Extensions

A127890 Largest n-digit right-truncatable prime.

Views

Author

Keywords

Comments

References

Links

Crossrefs

Programs

PARI

A100893 a(n) = smallest n-digit prime formed by appending a digit to a(n-1); a(1) = 2.

Views

Author

Keywords

Comments

Examples