Logo

Greetings from The On-Line Encyclopedia of Integer Sequences!

Hints

Search: id:A105720
Displaying 1-1 of 1 results found. page 1
     Format: long | short | internal | text      Sort: relevance | references | number      Highlight: on | off
A105720 Triangular matchstick numbers in the class of prime numbers: sum of n-th and next n primes. +0
1
5, 15, 36, 67, 112, 169, 240, 323, 424, 539, 662, 803, 964, 1133, 1312, 1523, 1746, 1987, 2246, 2519, 2808, 3119, 3436, 3787, 4154, 4529, 4920, 5337, 5770, 6219, 6682, 7173, 7672, 8203, 8760, 9323, 9912, 10517, 11140, 11783, 12450, 13135, 13836 (list; graph; listen)
OFFSET

1,1

COMMENT

Cf. A045943 Triangular matchstick numbers: sum of n and next n integers; a(n) are full squares at only(?) three values of n = 3, 6, 4072: {6,13,15735}^2;a(n) are primes at many values of for n = 1,4,16,18,22,36,40,44,52,...: 5,67,1523,1987,3119,9323,11783,14551,21019,...

FORMULA

a(n)=p(n)+p(n+1)+...+p(2n-1)+p(2n), p(k)=k-th prime

MATHEMATICA

a[n_]:=Plus@@Prime[Range[n, 2n]]

CROSSREFS

Cf. A045943.

Sequence in context: A056413 A032276 A065780 this_sequence A011933 A093802 A006008

Adjacent sequences: A105717 A105718 A105719 this_sequence A105721 A105722 A105723

KEYWORD

nonn

AUTHOR

Zak Seidov (zakseidov(AT)yahoo.com), May 04 2005

page 1

Search completed in 0.002 seconds

Lookup | Welcome | Find friends | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Transforms | Puzzles | Hot | Classics
More pages | Superseeker | Maintained by N. J. A. Sloane (njas@research.att.com)

Last modified August 30 13:03 EDT 2008. Contains 143253 sequences.


AT&T Labs Research