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.

A286816 Smallest b such that the k consecutive primes starting with prime(n) are all base-b Wieferich primes, i.e., satisfy b^(p-1) == 1 (mod p^2). Square array A(n, k), read by antidiagonals downwards.

Original entry on oeis.org

5, 17, 8, 449, 26, 7, 557, 226, 18, 18, 19601, 1207, 1207, 148, 3, 132857, 54568, 1451, 606, 239, 19, 4486949, 2006776, 13543, 13543, 3469, 249, 38, 126664001, 20950343, 296449, 296449, 24675, 653, 423, 28, 2363321449, 230695118, 23250274, 17134811, 3414284, 39016, 5649, 28, 28, 5229752849, 5229752849, 882345432, 741652533, 36763941, 14380864, 217682, 26645, 63, 14
Offset: 1

Views

Author

Felix Fröhlich, May 27 2017

Keywords

Examples

			The sequence of base-226 Wieferich primes starts 3, 5, 7, 97, 157, ... Since 226 is the smallest b such that the three consecutive primes starting with prime(2) = 3 are base-b Wieferich primes, A(2, 3) = 226.
Array starts:
n=1: 5, 17, 449, 557, 19601, 132857
n=2: 8, 26, 226, 1207, 54568, 2006776
n=3: 7, 18, 1207, 1451, 13543, 296449
n=4: 18, 148, 606, 13543, 296449, 17134811
n=5: 3, 239, 3469, 24675, 3414284, 36763941
n=6: 19, 249, 653, 39016, 14380864, 34998229
		

Crossrefs

Columns: A039678 (k=1), A259075 (k=2), A344827 (k=3), A344828 (k=4), A344829 (k=5), A344830 (k=6), A344831 (k=7), A344832 (k=8).
Cf. A256236 (row n=1), A258787.

Programs

  • PARI
    primevec(initialp, vecsize) = my(v=[initialp]); while(#v < vecsize, v=concat(v, nextprime(v[#v]+1))); v
    a(n, k) = my(v=primevec(prime(n), k), b=2, i=0); while(1, for(x=1, #v, if(Mod(b, v[x]^2)^(v[x]-1)!=1, i++; break)); if(i==0, return(b)); b++; i=0)
    array(rows, cols) = for(s=1, rows, for(t=1, cols, print1(a(s, t), ", ")); print(""))
    array(5, 6) \\ print 5 X 6 array

Extensions

More terms from Max Alekseyev, Oct 10 2023

A344828 a(n) is the smallest b > 1 such that prime(n), prime(n+1), prime(n+2) and prime(n+3) are all base-b Wieferich primes.

Original entry on oeis.org

557, 1207, 1451, 13543, 24675, 39016, 217682, 165407, 1357748, 399254, 1146590, 325346, 1895206, 3365181, 4674177, 21251205, 40698745, 6795147, 36463448, 12717474, 54383927, 7411274, 35989426, 101112784, 86045167, 13128506, 276293632, 169093089, 223680564, 137073637
Offset: 1

Views

Author

Felix Fröhlich, May 29 2021

Keywords

Crossrefs

Cf. A039678, A259075. Column 4 of A286816.
Cf. smallest b > 1 such that prime(n+i) is a base-b Wieferich prime for each i = 0..k: A039678 (k=0), A259075 (k=1), A344827 (k=2), A344829 (k=4), A344830 (k=5), A344831 (k=6), A344832 (k=7).

Programs

  • PARI
    a(n) = my(v=[prime(n)]); while(#v < 4, v=concat(v, nextprime(v[#v]+1))); for(b=2, oo, for(k=1, #v, if(Mod(b, v[k]^2)^(v[k]-1)!=1, break, if(k==#v, return(b)))))

Extensions

Terms a(24) onward from Max Alekseyev, Oct 10 2023

A344830 a(n) is the smallest b > 1 such that prime(n), prime(n+1), prime(n+2), prime(n+3), prime(n+4) and prime(n+5) are all base-b Wieferich primes.

Original entry on oeis.org

132857, 2006776, 296449, 17134811, 36763941, 34998229, 31239565, 968576295, 1027038511, 287811239, 15022368222, 33452659960, 19477999997, 132892045949, 47341045210, 32176849766, 106967760951, 303459122992, 20216391690, 1411108384416, 219517083156, 361244580521, 455588981749
Offset: 1

Views

Author

Felix Fröhlich, May 29 2021

Keywords

Crossrefs

Cf. A039678, A259075. Column 6 of A286816.
Cf. smallest b > 1 such that prime(n+i) is a base-b Wieferich prime for each i = 0..k: A039678 (k=0), A259075 (k=1), A344827 (k=2), A344828 (k=3), A344829 (k=4), A344831 (k=6), A344832 (k=7).

Programs

  • PARI
    a(n) = my(v=[prime(n)]); while(#v < 6, v=concat(v, nextprime(v[#v]+1))); for(b=2, oo, for(k=1, #v, if(Mod(b, v[k]^2)^(v[k]-1)!=1, break, if(k==#v, return(b)))))

Extensions

Terms a(10) onward from Max Alekseyev, Oct 10 2023

A344831 a(n) is the smallest b > 1 such that prime(n), prime(n+1), prime(n+2), prime(n+3), prime(n+4), prime(n+5) and prime(n+6) are all base-b Wieferich primes.

Original entry on oeis.org

4486949, 20950343, 23250274, 741652533, 710808570, 2380570527, 4967352848, 39489360341, 6143373023, 64470545267, 627069771908, 407165268367, 676579634125, 676579634125, 2923957743077, 369072416795, 5110842013966, 19645397150616, 16037329738682, 5867065121893, 31015370285102
Offset: 1

Views

Author

Felix Fröhlich, May 29 2021

Keywords

Comments

Surprisingly, we have a(13) = a(14) = A344832(13). - Max Alekseyev, Oct 10 2023

Crossrefs

Cf. A039678, A259075. Column 7 of A286816.
Cf. smallest b > 1 such that prime(n+i) is a base-b Wieferich prime for each i = 0..k: A039678 (k=0), A259075 (k=1), A344827 (k=2), A344828 (k=3), A344829 (k=4), A344830 (k=5), A344832 (k=7).

Programs

  • PARI
    a(n) = my(v=[prime(n)]); while(#v < 7, v=concat(v, nextprime(v[#v]+1))); for(b=2, oo, for(k=1, #v, if(Mod(b, v[k]^2)^(v[k]-1)!=1, break, if(k==#v, return(b)))))

Extensions

Terms a(8) onward from Max Alekseyev, Oct 10 2023

A344832 a(n) is the smallest b > 1 such that prime(n), prime(n+1), prime(n+2), prime(n+3), prime(n+4), prime(n+5), prime(n+6) and prime(n+7) are all base-b Wieferich primes.

Original entry on oeis.org

126664001, 230695118, 882345432, 12106746963, 93732236423, 66888229817, 84391291750, 3685694924698, 4506100208066, 1058174730735, 3827951700972, 58674393094169, 676579634125, 83450880181400, 100819901293157, 365919682326848, 695001153578920, 1046021079620904, 2989564836636529, 3724954519064878
Offset: 1

Views

Author

Felix Fröhlich, May 29 2021

Keywords

Crossrefs

Cf. A039678, A259075. Column 8 of A286816.
Cf. smallest b > 1 such that prime(n+i) is a base-b Wieferich prime for each i = 0..k: A039678 (k=0), A259075 (k=1), A344827 (k=2), A344828 (k=3), A344829 (k=4), A344830 (k=5), A344831 (k=6).

Programs

  • PARI
    a(n) = my(v=[prime(n)]); while(#v < 8, v=concat(v, nextprime(v[#v]+1))); for(b=2, oo, for(k=1, #v, if(Mod(b, v[k]^2)^(v[k]-1)!=1, break, if(k==#v, return(b)))))

Extensions

Terms a(5) onward from Max Alekseyev, Oct 10 2023

A344827 a(n) is the smallest b > 1 such that prime(n), prime(n+1) and prime(n+2) are all base-b Wieferich primes.

Original entry on oeis.org

449, 226, 1207, 606, 3469, 653, 5649, 26645, 7805, 6154, 36088, 14368, 49662, 66565, 153463, 40667, 760637, 31871, 265418, 411467, 484205, 148989, 688285, 796095, 1920186, 747071, 3516680, 569812, 905979, 3193580, 3303343, 1967646, 1728157, 4436267, 912246
Offset: 1

Views

Author

Felix Fröhlich, May 29 2021

Keywords

Crossrefs

Cf. A039678, A259075. Column 3 of A286816.
Cf. smallest b > 1 such that prime(n+i) is a base-b Wieferich prime for each i = 0..k: A039678 (k=0), A259075 (k=1), A344828 (k=3), A344829 (k=4), A344830 (k=5), A344831 (k=6), A344832 (k=7).

Programs

  • PARI
    a(n) = my(v=[prime(n)]); while(#v < 3, v=concat(v, nextprime(v[#v]+1))); for(b=2, oo, for(k=1, #v, if(Mod(b, v[k]^2)^(v[k]-1)!=1, break, if(k==#v, return(b)))))
Showing 1-6 of 6 results.