A186506 An example of a pyramid of numbers that starts with 1 and successive terms are primes formed by inserting the next power of 3 somewhere in the previous term.

1, 13, 139, 12739, 1281739, 1281739243, 1281737299243, 12817372218799243, 128173765612218799243, 12196838173765612218799243, 1219683817376590495612218799243, 1219683817714717376590495612218799243, 1219683853144117714717376590495612218799243, 12196838531441159432317714717376590495612218799243, 121968385314411594323177147478296917376590495612218799243

Offset

0,2

Comments

This is not really well-defined, but it is a published sequence of some recreational interest.

References

C. K. Caldwell and A. Rupinski, Pyramids of 3-powerful primes, Mathematical Spectrum, 43 (No. 2, 2010/2011), 65-69.

Links

Table of n, a(n) for n=0..14.

C. K. Caldwell and A. Rupinski, Pyramids of 3-powerful primes (abstract), Mathematical Spectrum, 43 (No. 2, 2010/2011), 65-69.

Example

(1)
13
139
12739
1281739
1281739243
1281737299243
12817372218799243
128173765612218799243
12196838173765612218799243
1219683817376590495612218799243
1219683817714717376590495612218799243
1219683853144117714717376590495612218799243
12196838531441159432317714717376590495612218799243
121968385314411594323177147478296917376590495612218799243

Crossrefs

Cf. A186507.

Sequence in context: A365999 A064103 A266630 * A051639 A138931 A157160

Adjacent sequences: A186503 A186504 A186505 * A186507 A186508 A186509

Keyword

base,nonn,fini,full

Author

N. J. A. Sloane, Feb 22 2011

Status

approved