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.

Showing 1-6 of 6 results.

A133427 Records in A025017.

Original entry on oeis.org

4, 6, 12, 30, 124, 418, 1274, 2512, 3526, 4618, 7432, 12778, 26098, 34192, 37768, 59914, 88786, 97768, 112558, 221942, 237544, 485326, 642358, 686638, 1042078, 1172918, 2041402, 2406448, 4288574, 4938848, 9292156, 14341888, 17726098, 20757292, 32507242
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2007

Keywords

Links

A133428 Where records occur in A025017.

Original entry on oeis.org

1, 2, 3, 4, 5, 7, 12, 16, 17, 20, 23, 24, 26, 32, 35, 39, 41, 43, 45, 48, 55, 56, 60, 66, 69, 75, 79, 81, 90, 93, 97, 98, 104, 108, 120, 131, 132, 135, 137, 146, 147, 156, 160, 165, 173, 176, 178, 182, 184, 208, 212, 217, 226, 228, 230, 238, 246, 248, 277, 280, 285, 287, 290
Offset: 1

Views

Author

N. J. A. Sloane, Nov 28 2007

Keywords

Links

A102043 Duplicate of A025017.

Original entry on oeis.org

4, 6, 12, 30, 124, 122, 418, 98, 220, 346, 308, 1274, 1144, 962, 556, 2512, 3526, 1382
Offset: 1

Views

Author

Keywords

A051169 Smallest number m such that 2*m - p is composite for the first n primes p.

Original entry on oeis.org

3, 6, 15, 49, 49, 49, 49, 110, 154, 154, 278, 278, 278, 278, 496, 496, 496, 496, 496, 496, 1321, 1321, 1321, 1321, 1321, 1321, 2686, 2686, 2686, 2686, 2686, 2686, 2686, 3713, 3713, 3713, 3713, 3713, 3713, 21766, 21766, 21766, 21766, 21766, 21766, 21766
Offset: 1

Views

Author

Paul S. Bruckman (pbruckman(AT)hotmail.com)

Keywords

Examples

			a(2) = 6 because 2*6-2 = 10 and 2*6-3 = 9 are composite.

References

  • Computed by Peter G. Anderson at the Rochester Institute of Technology.

Links

Crossrefs

See A051610 and A116111 for records. Cf. A025017.
Cf. A010051, A000040.

Programs

  • Haskell
    a051169 n = head [m | m <- [2..],
            all (== 0) $ map (a010051' . (2*m -)) $ take n a000040_list]
-- Reinhard Zumkeller, Apr 09 2015
  • Mathematica
    a[n_] := a[n] = Catch[For[m = 2, True, m++, If[And @@ (! PrimeQ[2*m - #] &) /@ Prime /@ Range[n], Throw[m]]]]; Table[ Print[a[n]]; a[n], {n, 1, 46}] (* Jean-François Alcover, Jul 17 2012 *)
Module[{nn=50,prs},prs=Prime[Range[nn]];Table[SelectFirst[Range[50000], AllTrue[Table[2#-p,{p,Take[prs,n]}],CompositeQ]&],{n,nn}]] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 18 2015 *)

Extensions

More terms from Paul S. Bruckman, Jan 20 2007
Edited by N. J. A. Sloane, Apr 14 2007, May 04 2007, Jun 10 2008

A103508 a(n) = 1 + 2 * least i such that A103507(i)=n+1, 0 if no such i exists.

Original entry on oeis.org

9, 15, 31, 101, 139, 227, 91, 503, 995, 451, 751, 539, 1819, 1397, 2957, 3461, 1831, 1417, 6023, 3769, 1777, 9587, 5411, 9421, 18653, 8089, 4511, 6541, 10529, 16051, 19049, 13163, 3139, 22937, 23929, 43363, 24919, 43571, 97367, 55571, 14419, 75209
Offset: 1

Views

Author

Lei Zhou, Feb 10 2005

Keywords

Crossrefs

Cf. A103510, A103151, A103152, A103153, A103506, A103507, A025017.

Programs

  • Scheme
    (define (A103508 n) (+ 1 (* 2 (first-n-where-fun_n-is-i1 A103507 (+ 1 n)))))
(define (first-n-where-fun_n-is-i1 fun i) (let loop ((n 1)) (cond ((= i (fun n)) n) (else (loop (+ n 1))))))

Extensions

Edited and Scheme-code added by Antti Karttunen, Jun 19 2007

A103510 a(n) = 1 + 2 * least i such that A103509(i)=n+1, 0 if no such i exists.

Original entry on oeis.org

9, 11, 21, 57, 23, 55, 245, 241, 115, 833, 83, 523, 437, 193, 447, 733, 167, 689, 1417, 611, 2297, 1081, 2731, 1283, 2755, 5057, 2761, 887, 2719, 9221, 4909, 8179, 4397, 13891, 9557, 2351, 9257, 5869, 10627, 11941, 1487, 2797, 3947, 5899, 11237, 20069
Offset: 1

Views

Author

Lei Zhou, Feb 10 2005

Keywords

Crossrefs

Cf. A103508, A103151, A103152, A103153, A103506, A103509, A025017.

Programs

  • Mathematica
    Array[a, 500]; Do[a[n] = 0, {n, 1, 500}]; n = 9; ct = 0; While[ct < 150, m = 3; While[ ! (PrimeQ[m] && (((n - m)/2) > 2) && PrimeQ[(n - m)/2]), m = m + 2]; k = PrimePi[m]; If[a[k] == 0, a[k] = n; ct = ct + 1]; n = n + 2]; Print[a]
  • Scheme
    (define (A103510 n) (+ 1 (* 2 (first-n-where-fun_n-is-i1 A103509 (+ 1 n)))))
(define (first-n-where-fun_n-is-i1 fun i) (let loop ((n 1)) (cond ((= i (fun n)) n) (else (loop (+ n 1))))))

Extensions

Edited and Scheme-code added by Antti Karttunen, Jun 19 2007
Showing 1-6 of 6 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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