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.

A138833 Concatenation of n-th perfect number and n-th Mersenne prime A000668(n).

Original entry on oeis.org

63, 287, 49631, 8128127, 335503368191, 8589869056131071, 137438691328524287, 23058430081399521282147483647, 26584559915698317446546926159538421762305843009213693951, 191561942608236107294793378084303638130997321548169216618970019642690137449562111
Offset: 1

Views

Author

Omar E. Pol, Apr 06 2008

Keywords

Comments

a(15) has 1156 digits. - Harvey P. Dale, Jan 10 2023

Examples

			a(3)=49631 because A000396(3)=496 and A000668(3)=31.

Links

Crossrefs

Cf. A000396, A000668, A138816, A138817, A138818, A138819, A138820, A138821, A138822, A138832.

Programs

  • Mathematica
    Module[{nn=10},FromDigits[Flatten[IntegerDigits/@#]]&/@Thread[{PerfectNumber[ Range[ nn]],2^ MersennePrimeExponent[ Range[nn]]-1}]] (* Harvey P. Dale, Jan 10 2023 *)

Extensions

Corrected and extended by Harvey P. Dale, Jan 10 2023

A139114 Concatenation of n-th Fibonacci number and n.

Original entry on oeis.org

11, 12, 23, 34, 55, 86, 137, 218, 349, 5510, 8911, 14412, 23313, 37714, 61015, 98716, 159717, 258418, 418119, 676520, 1094621, 1771122, 2865723, 4636824, 7502525, 12139326, 19641827, 31781128, 51422929, 83204030, 134626931, 217830932
Offset: 1

Views

Author

Omar E. Pol, Apr 09 2008

Keywords

Links

Crossrefs

Cf. A000027, A000045, A045532, A075110, A138821, A138822, A139113.

Programs

  • Mathematica
    #[[1]]*10^IntegerLength[#[[2]]]+#[[2]]&/@Table[{Fibonacci[n],n},{n,40}] (* Harvey P. Dale, Nov 03 2016 *)

A253910 Concatenation of n-th prime and n-th nonprime.

Original entry on oeis.org

21, 34, 56, 78, 119, 1310, 1712, 1914, 2315, 2916, 3118, 3720, 4121, 4322, 4724, 5325, 5926, 6127, 6728, 7130, 7332, 7933, 8334, 8935, 9736, 10138, 10339, 10740, 10942, 11344, 12745, 13146, 13748, 13949, 14950, 15151, 15752, 16354, 16755, 17356, 17957, 18158, 19160, 19362, 19763, 19964, 21165, 22366, 22768, 22969
Offset: 1

Views

Author

Omar E. Pol, Feb 06 2015

Keywords

Comments

Concatenate A000040(n) and A018252(n).

Examples

			a(5) = 119 because the 5th prime is 11 and the 5th nonprime is 9.

Links

Crossrefs

Cf. A000040, A018252, A038530, A045532, A075110, A106582, A138821, A138822, A253911.

Programs

  • Haskell
    import Data.Function (on)
a253911 n = a253911_list !! (n-1)
a253911_list = map read $
   zipWith ((++) `on` show) a018252_list a000040_list :: [Integer]
-- Reinhard Zumkeller, Feb 09 2015
  • PARI
    nprime(n)=c=0;k=1;while(k,if(!isprime(k),c++);if(c==n,return(k));k++)
vector(50,n,eval(concat(Str(prime(n)),Str(nprime(n))))) \\ Derek Orr, Feb 06 2015

A253911 Concatenation of n-th nonprime and n-th prime.

Original entry on oeis.org

12, 43, 65, 87, 911, 1013, 1217, 1419, 1523, 1629, 1831, 2037, 2141, 2243, 2447, 2553, 2659, 2761, 2867, 3071, 3273, 3379, 3483, 3589, 3697, 38101, 39103, 40107, 42109, 44113, 45127, 46131, 48137, 49139, 50149, 51151, 52157, 54163, 55167, 56173, 57179, 58181, 60191, 62193, 63197, 64199, 65211, 66223, 68227, 69229
Offset: 1

Views

Author

Omar E. Pol, Feb 06 2015

Keywords

Comments

Concatenate A018252(n) and A000040(n).

Examples

			a(5) = 911 because the 5th nonprime is 9 and the 5th prime is 11.

Links

Crossrefs

Cf. A000040, A018252, A038530, A045532, A075110, A106582, A138821, A138822, A253910.

Programs

  • Haskell
    import Data.Function (on)
a253911 n = a253911_list !! (n-1)
a253911_list = map read $
   zipWith ((++) `on` show) a018252_list a000040_list :: [Integer]
-- Reinhard Zumkeller, Feb 09 2015
  • Mathematica
    cncat[{a_,b_}]:=FromDigits[Flatten[IntegerDigits/@{a,b}]]; Module[ {nn=100,np,len},np = Select[Range[nn],!PrimeQ[#]&];len=Length[np];cncat/@Thread[{np,Prime[Range[len]]}]] (* Harvey P. Dale, Oct 17 2020 *)
  • PARI
    nprime(n)=c=0; k=1; while(k, if(!isprime(k), c++); if(c==n, return(k)); k++)
vector(50, n, eval(concat(Str(nprime(n)), Str(prime(n))))) \\ Derek Orr, Feb 06 2015

A138832 Concatenation of n-th Mersenne prime A000668(n) and n-th perfect number.

Original entry on oeis.org

36, 728, 31496, 1278128, 819133550336, 1310718589869056, 524287137438691328, 21474836472305843008139952128, 23058430092136939512658455991569831744654692615953842176
Offset: 1

Views

Author

Omar E. Pol, Apr 06 2008

Keywords

Examples

			a(3)=31496 because A000668(3)=31 and A000396(3)=496.

Crossrefs

Cf. A000396, A000668, A138816, A138817, A138818, A138819, A138820, A138821, A138822, A138833.

A139113 Concatenation of n and n-th Fibonacci number.

Original entry on oeis.org

11, 21, 32, 43, 55, 68, 713, 821, 934, 1055, 1189, 12144, 13233, 14377, 15610, 16987, 171597, 182584, 194181, 206765, 2110946, 2217711, 2328657, 2446368, 2575025, 26121393, 27196418, 28317811, 29514229, 30832040, 311346269, 322178309
Offset: 1

Views

Author

Omar E. Pol, Apr 09 2008

Keywords

Crossrefs

Cf. A000027, A000045, A045532, A075110, A138821, A138822, A139114.

Programs

  • Mathematica
    Table[FromDigits[Join[IntegerDigits[n],IntegerDigits[Fibonacci[n]]]],{n,40}] (* Harvey P. Dale, Dec 31 2015 *)
Showing 1-6 of 6 results.

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

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