This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A092696 Smoothly undulating palindromic primes of the form (12*10^n-21)/99. 4
 1212121, 12121212121, 1212121212121212121212121212121212121212121 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The De Geest link calls these smoothly undulating palindromic primes. Corresponding n are given in A062209. Equivalently, primes of the form 1212...121: Decimal digits "12" repeated k times with 1 appended (or "21" repeated k times with 1 prefixed). Corresponding k are given in A056803. The next term, a(4), has "12" repeating A056803(4) = 69 times and length A062209(4) = 2*A056803(4) + 1 = 139 decimal digits. LINKS P. De Geest, SUPP Reference Table FORMULA a(n) = (4*10^A062209(n)-7)/33. - M. F. Hasler, Jul 30 2015 CROSSREFS Cf. A056803 (number of 12's (or 21's)), A062209 (corresponding decimal digit lengths). Cf. A032758, A033619, A030291, A059168, A242541, A004022. Sequence in context: A251166 A274833 A206042 * A203627 A235910 A234997 Adjacent sequences:  A092693 A092694 A092695 * A092697 A092698 A092699 KEYWORD bref,nonn,base AUTHOR Rick L. Shepherd, Mar 04 2004 EXTENSIONS Edited by M. F. Hasler, Jul 30 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 24 12:21 EDT 2019. Contains 322429 sequences. (Running on oeis4.)