cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A069484 a(n) = prime(n+1)^2 + prime(n)^2.

Original entry on oeis.org

13, 34, 74, 170, 290, 458, 650, 890, 1370, 1802, 2330, 3050, 3530, 4058, 5018, 6290, 7202, 8210, 9530, 10370, 11570, 13130, 14810, 17330, 19610, 20810, 22058, 23330, 24650, 28898, 33290, 35930, 38090, 41522, 45002
Offset: 1

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Author

Reinhard Zumkeller, Mar 29 2002

Keywords

Comments

Together with A069482(n) and A069486(n) a Pythagorean triangle is formed with area = A069487(n).

Crossrefs

Programs

Formula

a(n) = A001248(n+1) + A001248(n) = A000040(n+1)^2 + A000040(n)^2.
a(n) = A048851(n+1).
a(n) = 2 * A075892(n) for n > 1.

A048852 Difference between b^2 (in c^2=a^2+b^2) and product of successive prime pairs.

Original entry on oeis.org

0, 3, 10, 14, 44, 26, 68, 38, 92, 174, 62, 222, 164, 86, 188, 318, 354, 122, 402, 284, 146, 474, 332, 534, 776, 404, 206, 428, 218, 452, 1778, 524, 822, 278, 1490, 302, 942, 978, 668, 1038, 1074, 362, 1910, 386, 788, 398, 2532, 2676, 908, 458, 932, 1434, 482
Offset: 0

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Author

Keywords

Examples

			a(3)=10. Product of 3rd prime pair 3*5=15 (after 2*2=4 and 2*3=6). b^2=25 (in c^2=a^2+b^2) where c^2=34 and a^2=9. Then 25-15=10.
		

Crossrefs

Programs

  • Magma
    [0] cat [NthPrime(n+1)*(NthPrime(n+1)-NthPrime(n)): n in [1..60]]; // G. C. Greubel, Feb 22 2024
    
  • Mathematica
    With[{P=Prime}, Table[If[n==0, 0, P[n+1]*(P[n+1]-P[n])], {n,0,60}]] (* G. C. Greubel, Feb 22 2024 *)
  • SageMath
    p=nth_prime; [0]+[p(n+1)*(p(n+1)-p(n)) for n in range(1,61)] # G. C. Greubel, Feb 22 2024

Formula

Find b^2 in Pythagorean formula c^2=a^2+b^2. Subtract product of successive prime pair at same a(n) beginning at 2*2.
For n>0, a(n) = A000040(n+1)^2 - A000040(n) * A000040(n+1). - Mamuka Jibladze, Mar 24 2017

A048871 Length of hypotenuse squared in right triangle formed by a palindromic spiral plotted in Cartesian coordinates.

Original entry on oeis.org

2, 5, 13, 25, 41, 61, 85, 113, 145, 202, 605, 1573, 3025, 4961, 7381, 10285, 13673, 17545, 20002, 22522, 26962, 31802, 37042, 42682, 48722, 55162, 62002, 69242, 77285, 85748, 94228, 103108, 112388, 122068, 132148, 142628, 153508, 164788
Offset: 1

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Author

Keywords

Examples

			To begin palindromic spiral, plot (1, 0), (0, 1). Hypotenuse is c^2=a^2+b^2, or 2=1+1. a(1) = 2.
a(2)=5 because c^2=a^2+b^2 and 5=1+4.
		

References

  • H. E. Huntley, The Divine Proportion, A Study in Mathematical Beauty. New York: Dover, 1970. See Chapter 13, Spira Mirabilis, especially Fig. 13-5, page 173.

Crossrefs

Cf. A002113.
An analog of the prime spiral of A048851.

Programs

  • Mathematica
    Join[{2},Total[#^2]&/@Partition[Select[Range[300],PalindromeQ],2,1]] (* Harvey P. Dale, Mar 18 2024 *)

Formula

a(n) = A002113(n)^2 + A002113(n-1)^2, n > 1.
Showing 1-3 of 3 results.