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.

Previous Showing 11-16 of 16 results.

A038451 Sums of 9 distinct powers of 10.

Original entry on oeis.org

111111111, 1011111111, 1101111111, 1110111111, 1111011111, 1111101111, 1111110111, 1111111011, 1111111101, 1111111110, 10011111111, 10101111111, 10110111111, 10111011111, 10111101111, 10111110111, 10111111011
Offset: 1

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Author

Keywords

Crossrefs

Programs

  • Mathematica
    Sort[Plus @@@ Subsets[10^Range[0, 10], {9}]] (* Amiram Eldar, Jul 12 2022 *)
  • Python
    from itertools import islice
    def A038451_gen(): # generator of terms
        yield int(bin(n:=511)[2:])
        while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:])
    A038451_list = list(islice(A038451_gen(),20)) # Chai Wah Wu, Mar 11 2025

Extensions

Offset corrected by Amiram Eldar, Jul 12 2022

A038467 Sums of 5 distinct powers of 3.

Original entry on oeis.org

121, 283, 337, 355, 361, 363, 769, 823, 841, 847, 849, 985, 1003, 1009, 1011, 1057, 1063, 1065, 1081, 1083, 1089, 2227, 2281, 2299, 2305, 2307, 2443, 2461, 2467, 2469, 2515, 2521, 2523, 2539, 2541, 2547, 2929, 2947, 2953, 2955, 3001, 3007, 3009, 3025, 3027, 3033
Offset: 1

Views

Author

Keywords

Crossrefs

Base 3 interpretation of A038447.

Programs

  • Mathematica
    Union[Total/@Subsets[3^Range[0,7],{5}]]  (* Harvey P. Dale, Feb 23 2011 *)

A038473 Sums of 5 distinct powers of 4.

Original entry on oeis.org

341, 1109, 1301, 1349, 1361, 1364, 4181, 4373, 4421, 4433, 4436, 5141, 5189, 5201, 5204, 5381, 5393, 5396, 5441, 5444, 5456, 16469, 16661, 16709, 16721, 16724, 17429, 17477, 17489, 17492, 17669, 17681, 17684, 17729, 17732, 17744, 20501, 20549, 20561, 20564, 20741
Offset: 1

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Author

Keywords

Crossrefs

Base 4 interpretation of A038447.

Programs

  • Mathematica
    Take[Total/@Subsets[4^Range[0,10],{5}]//Union,50] (* Harvey P. Dale, Oct 02 2016 *)
  • Python
    from itertools import islice
    def A038473_gen(): # generator of terms
        yield int(bin(n:=31)[2:],4)
        while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:],4)
    A038473_list = list(islice(A038473_gen(),30)) # Chai Wah Wu, Apr 04 2025

A038477 Sums of 5 distinct powers of 5.

Original entry on oeis.org

781, 3281, 3781, 3881, 3901, 3905, 15781, 16281, 16381, 16401, 16405, 18781, 18881, 18901, 18905, 19381, 19401, 19405, 19501, 19505, 19525, 78281, 78781, 78881, 78901, 78905, 81281, 81381, 81401, 81405, 81881, 81901, 81905, 82001, 82005, 82025, 93781, 93881, 93901
Offset: 1

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Author

Keywords

Crossrefs

Base 5 interpretation of A038447.

Programs

  • Mathematica
    Union[Total[5^#]&/@Subsets[Range[0,8],{5}]] (* Harvey P. Dale, Nov 15 2012 *)
  • Python
    from itertools import islice
    def A038477_gen(): # generator of terms
        yield int(bin(n:=31)[2:],5)
        while True: yield int(bin((n:=n^((a:=-n&n+1)|(a>>1)) if n&1 else ((n&~(b:=n+(a:=n&-n)))>>a.bit_length())^b))[2:],5)
    A038477_list = list(islice(A038477_gen(),30)) # Chai Wah Wu, Apr 05 2025

Extensions

Offset corrected by Amiram Eldar, Jul 13 2022

A383918 Primes made up of 0's and five 1's only.

Original entry on oeis.org

101111, 10011101, 10101101, 10110011, 10111001, 11000111, 11100101, 100100111, 100111001, 101001011, 101100011, 110010101, 110101001, 111000101, 111001001, 1000011011, 1000110101, 1001000111, 1001001011, 1001010011, 1010000111, 1010001101, 1010010011, 1010100011, 1010110001
Offset: 1

Views

Author

René-Louis Clerc, May 15 2025

Keywords

Comments

Expression of the primes that are 0-successors of the preprime 11111 (= 41*271); they constitute the infinite set of secondary primes with five 1's and zeros denoted {11111} (Definitions 1, 2, 3, 4 of Clerc).

Crossrefs

Programs

  • Maple
    f:= proc(n) local R,c,i;
     sort(select(isprime, [seq(1+10^(n-1) + add(10^i,i=c), c=combinat:-choose(n-2,3))]))
    end proc:
    map(op,[seq(f(i),i=6..10)]); # Robert Israel, May 29 2025
  • PARI
    list(M) = for(i=3, M, for(j=2, i-1, for(k=1, j-1, for(r=1, k-1, my(p=10^i+10^j+10^k+10^r+1); isprime(p) && print1(p, ", ")))))
    
  • Python
    from itertools import count, islice
    from sympy import isprime
    def A383918_gen(): # generator of terms
        for a in count(4):
            for b in range(3,a):
                for c in range(2,b):
                    for d in range(1,c):
                        if isprime(p:=10**a+10**b+10**c+10**d|1):
                            yield(p)
    A383918_list = list(islice(A383918_gen(),30)) # Chai Wah Wu, May 29 2025

A383919 Primes made up of 0's and seven 1's only.

Original entry on oeis.org

11110111, 11111101, 101101111, 101111011, 110111011, 111010111, 1001110111, 1010011111, 1011110011, 1100101111, 1101010111, 1101110011, 1110011101, 1110110011, 1111100101, 1111110001, 10010110111, 10011101011, 10011110101, 10100111101, 10111001011, 10111110001, 11001011101
Offset: 1

Views

Author

René-Louis Clerc, May 15 2025

Keywords

Comments

Expression of the primes that are 0-successors of the preprime 1111111 (= 239*4649); they constitute the infinite set of secondary primes with seven 1's and zeros denoted {1111111} (Definitions 1, 2, 3, 4 of Clerc).

Crossrefs

Intersection of A020449 and A062337.

Programs

  • PARI
    list(M) = for(i=3, M, for(j=2, i-1, for(k=1, j-1, for(r=1, k-1, for(l=1, r-1, for(m=1, l-1, my(p=10^i+10^j+10^k+10^r+10^l+10^m+1); isprime(p) && print1(p, ", ")))))))
    
  • Python
    from itertools import count, islice
    from sympy import isprime
    def A383919_gen(): # generator of terms
        for a in count(6):
            for b in range(5,a):
                for c in range(4,b):
                    for d in range(3,c):
                        for e in range(2,d):
                            for f in range(1,e):
                                if isprime(p:=10**a+10**b+10**c+10**d+10**e+10**f|1):
                                    yield(p)
    A383919_list = list(islice(A383919_gen(),23)) # Chai Wah Wu, May 28 2025
Previous Showing 11-16 of 16 results.