The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A056221 Image of primes (A000040) under "little Hankel" transform that sends [c_0, c_1, ...] to [d_0, d_1, ...] where d_n = c_n^2 - c_{n+1}*c_{n-1}. 9
 -1, 4, -6, 30, -18, 42, -30, -22, 128, -112, 98, 90, -78, -70, 36, 248, -232, 158, 150, -280, 182, -142, -130, 420, 210, -198, 222, -210, -1074, 1326, -238, 560, -1092, 1212, -592, 36, 350, -310, 36, 728, -1428, 1548, -378, 402, -1966, 144, 1832, 462, -450, -442 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(n) > 0 if and only if n+1 is in A046868. a(n) < 0 if and only if n+1 is in A233671. - Chai Wah Wu, Sep 10 2019 LINKS Table of n, a(n) for n=1..50. L. Panaitopol, On the sequence p(n)^2=p(n-1)*p(n+1), J. Inequal. Pure Appl. Math., Volume 3, Issue 4, Article 53, 2002. FORMULA a(n) = determinant of matrix | prime(n+1) prime(n)| | prime(n+2) prime(n+1)|. - Zak Seidov, Jul 23 2008, indices corrected by Gary Detlefs, Dec 09 2011 a(n) = 2*A342567(n+1) for n >= 2. - Hugo Pfoertner, Jun 20 2021 MAPLE A056221 := proc(n) ithprime(n+1)^2-ithprime(n)*ithprime(n+2) ; end proc: seq(A056221(n), n=1..10) ; # R. J. Mathar, Dec 10 2011 CROSSREFS Cf. A046868, A233671, A342567. Sequence in context: A142859 A259087 A364737 * A046849 A090530 A154667 Adjacent sequences: A056218 A056219 A056220 * A056222 A056223 A056224 KEYWORD sign AUTHOR N. J. A. Sloane, Aug 06 2000 STATUS approved

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

Last modified October 2 17:28 EDT 2023. Contains 365837 sequences. (Running on oeis4.)