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

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A062021 a(n) = Sum_{i=1..n} Sum_{j=1..i} (prime(i)^2 - prime(j)^2). 3

%I #13 May 04 2022 08:28:07

%S 0,5,42,151,548,1185,2542,4403,7608,13621,20834,32535,47980,65609,

%T 88278,119947,162368,208869,269194,340007,416580,512305,622286,756003,

%U 925432,1114661,1314498,1537015,1771628,2031993,2393158,2786315

%N a(n) = Sum_{i=1..n} Sum_{j=1..i} (prime(i)^2 - prime(j)^2).

%H Robert Israel, <a href="/A062021/b062021.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = 2*a(n-1) - a(n-2) + (n-1)*(prime(n)^2 - prime(n-1)^2) with a(1) = 0, a(2) = 5.

%e a(3) = (5^2 - 2^2) + (5^2 - 3^2) + (3^2 - 2^2) = 42.

%p N:= 100: # for a(1)..a(N)

%p P2:= [seq(ithprime(i)^2,i=1..N)]:

%p DP2:= P2[2..-1]-P2[1..-2]:

%p A[1]:= 0: A[2]:= 5:

%p for n from 3 to N do A[n]:= 2*A[n-1]+(n-1)*DP2[n-1]-A[n-2] od:

%p seq(A[i],i=1..N); # _Robert Israel_, Feb 02 2020

%t RecurrenceTable[{a[1]==0,a[2]==5,a[n]==2a[n-1]-a[n-2]+(n-1)(Prime[n]^2 - Prime[n-1]^2)}, a, {n,40}] (* _Harvey P. Dale_, May 16 2019 *)

%o (Magma) [(&+[(&+[NthPrime(i)^2 - NthPrime(j)^2: j in [1..i]]): i in [1..n]]): n in [1..40]]; // _G. C. Greubel_, May 04 2022

%o (SageMath)

%o @CachedFunction

%o def a(n):

%o if (n<3): return 5*(n-1)

%o else: return 2*a(n-1) - a(n-2) + (n-1)*(nth_prime(n)^2 - nth_prime(n-1)^2)

%o [a(n) for n in (1..40)] # _G. C. Greubel_, May 04 2022

%Y Cf. A000040, A062020, A062022.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Jun 02 2001

%E More terms and formula from Larry Reeves (larryr(AT)acm.org), Jun 06 2001

%E Name edited by _G. C. Greubel_, May 04 2022

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 29 02:23 EDT 2024. Contains 371264 sequences. (Running on oeis4.)