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 1-4 of 4 results.

A249594 Positions of primes in A249054.

Original entry on oeis.org

2, 4, 7, 11, 12, 14, 17, 18, 19, 22, 23, 27, 30, 32, 34, 37, 38, 41, 42, 45, 47, 50, 51, 53, 54, 55, 58, 61, 64, 65, 68, 71, 72, 74, 75, 78, 80, 81, 84, 87, 89, 90, 94, 97, 100, 102, 105, 108, 109, 111, 113, 116, 117, 119, 120, 123, 125, 129, 133, 134, 135
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 03 2014

Keywords

Comments

A249054(a(n)) = A000040(n); sequence is strictly increasing, i.e. all primes occur in A249054 in natural order, see also A249595.

Links

Crossrefs

Cf. A000040, A026233, A049084, A239968, A249054, A249595 (complement).

Programs

  • Haskell
    import Data.List (elemIndex); import Data.Maybe (fromJust)
a249594 = (+ 1) . fromJust . (`elemIndex` a249054_list) . a000040

A249595 Positions of nonprimes in A249054.

Original entry on oeis.org

1, 3, 5, 6, 8, 9, 10, 13, 15, 16, 20, 21, 24, 25, 26, 28, 29, 31, 33, 35, 36, 39, 40, 43, 44, 46, 48, 49, 52, 56, 57, 59, 60, 62, 63, 66, 67, 69, 70, 73, 76, 77, 79, 82, 83, 85, 86, 88, 91, 92, 93, 95, 96, 98, 99, 101, 103, 104, 106, 107, 110, 112, 114, 115
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 03 2014

Keywords

Comments

A249054(a(n)) = A018252(n); sequence is strictly increasing, i.e. all nonprimes occur in A249054 in natural order, see also A249594.

Links

Crossrefs

Cf. A018252, A026233, A049084, A239968, A249054, A249594 (complement).

Programs

  • Haskell
    import Data.List (elemIndex); import Data.Maybe (fromJust)
a249595 = (+ 1) . fromJust . (`elemIndex` a249054_list) . a018252

A249571 Inverse permutation to A249054.

Original entry on oeis.org

1, 2, 4, 3, 7, 5, 11, 6, 8, 9, 12, 10, 14, 13, 15, 16, 17, 20, 18, 21, 24, 25, 19, 26, 28, 29, 31, 33, 22, 35, 23, 36, 39, 40, 43, 44, 27, 46, 48, 49, 30, 52, 32, 56, 57, 59, 34, 60, 62, 63, 66, 67, 37, 69, 70, 73, 76, 77, 38, 79, 41, 82, 83, 85, 86, 88, 42
Offset: 1

Views

Author

Reinhard Zumkeller, Nov 01 2014

Keywords

Links

Crossrefs

Cf. A249054.

Programs

  • Haskell
    import Data.List (elemIndex); import Data.Maybe (fromJust)
a249571 = (+ 1) . fromJust . (`elemIndex` a249054_list)

A249053 Defined by (i) a(1)=1; (ii) if you move a(n) steps to the right you must reach a prime; (iii) a(n) = smallest unused composite number greater than a(n-1), unless a(n) is required to be prime by (ii), in which case a(n) is the smallest unused prime greater than a(n-1).

Original entry on oeis.org

1, 2, 4, 5, 6, 8, 11, 12, 13, 14, 17, 18, 20, 23, 24, 25, 26, 29, 30, 31, 32, 37, 38, 41, 42, 44, 45, 47, 48, 53, 54, 55, 59, 60, 62, 63, 67, 68, 71, 72, 73, 74, 79, 80, 81, 82, 83, 84, 89, 90, 97, 98, 101, 102, 104, 105, 106, 108, 109, 110, 113, 114, 115
Offset: 1

Views

Author

N. J. A. Sloane, Nov 01 2014

Keywords

References

  • Eric Angelini, Posting to Sequence Fans Mailing List, Mar 17 2008 (the definition was clarified by Gabriel Cunningham).

Links

Crossrefs

See A249054 for another version.
Cf. A002808, A007918.

Programs

  • Haskell
    import Data.Map (singleton, findMin, delete, insert)
a249053 n = a249053_list !! (n-1)
a249053_list = 1 : f 1 1 a002808_list (singleton 1 1) where
   f x z cs m
     | k == x    = p : f (x + 1) p cs (insert (x + p) 0 $ delete x m)
     | otherwise = c : f (x + 1) c cs' (insert (x + c) 0 m)
     where p = a007918 z
           (c:cs') = dropWhile (<= z) cs
           (k,_) = findMin m
-- Reinhard Zumkeller, Nov 01 2014
Showing 1-4 of 4 results.

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

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