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 1-8 of 8 results.

A167844 Convex primes.

Original entry on oeis.org

101, 103, 107, 109, 113, 127, 137, 139, 149, 211, 223, 227, 229, 239, 307, 311, 313, 317, 337, 347, 349, 359, 401, 409, 419, 421, 433, 439, 449, 457, 503, 509, 521, 523, 547, 557, 569, 601, 607, 613, 617, 619, 631, 643, 647, 659, 701, 709, 719, 727, 733, 739
Offset: 1

Views

Author

Omar E. Pol, Nov 13 2009

Keywords

Comments

Primes in A135641.
Primes whose structure of digits represents a convex function or a convex object. In the graphic representation the points are connected by imaginary line segments from left to right.
See A246033 for a different notion of "convex prime". - N. J. A. Sloane, Jul 25 2017

Crossrefs

Programs

  • PARI
    \\ See Links section.

Extensions

More terms from Rémy Sigrist, Dec 15 2018

A167843 Obtuse-angled primes.

Original entry on oeis.org

113, 127, 137, 139, 149, 157, 167, 179, 199, 211, 223, 227, 229, 233, 239, 257, 269, 277, 311, 331, 337, 347, 349, 359, 367, 379, 389, 421, 431, 433, 443, 449, 457, 467, 479, 499, 521, 541, 557, 569, 577, 599, 631, 641, 643, 653, 661, 677, 733, 743, 751, 761
Offset: 1

Views

Author

Omar E. Pol, Nov 13 2009

Keywords

Comments

Primes in A135603.
Primes whose structure of digits represents an obtuse angle. The vertex is an internal digit. In the graphic representation the points are connected by imaginary line segments from left to right.

Crossrefs

Programs

  • Python
    # uses agen() from A135603
    from sympy import isprime
    g = filter(isprime, agen())
    print([next(g) for n in range(1, 53)]) # Michael S. Branicky, Aug 03 2022

Extensions

a(12) and beyond from Michael S. Branicky, Aug 03 2022

A167845 Concave primes.

Original entry on oeis.org

131, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 233, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 331, 353, 367, 373, 379, 383, 389, 397, 431, 443, 461, 463, 467, 479, 487, 491, 499, 541, 563, 571, 577, 587, 593, 599, 641, 653, 661, 673
Offset: 1

Views

Author

Omar E. Pol, Nov 13 2009

Keywords

Comments

Primes in A135642.
Primes whose structure of digits represents a concave function or a concave object. In the graphic representation the points are connected by imaginary line segments from left to right.

Crossrefs

Extensions

More terms from Max Alekseyev, Apr 24 2010

A167846 Concave-convex primes.

Original entry on oeis.org

1021, 1031, 1033, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097, 1103, 1109, 1151, 1153, 1163, 1171, 1181, 1187, 1193, 1201, 1213, 1217, 1223, 1229, 1277, 1279, 1283, 1289, 1291, 1297, 1301, 1303, 1307, 1319, 1327, 1361, 1367, 1373, 1381, 1399, 1409, 1423
Offset: 1

Views

Author

Omar E. Pol, Nov 13 2009

Keywords

Comments

Primes in A163278.
Prime numbers with more than three digits that are not straight-line numbers (A135643), concave numbers (A135642) or convex numbers (A135641).

Crossrefs

Extensions

More terms from Rémy Sigrist, May 22 2019

A167847 Straight-line primes.

Original entry on oeis.org

11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 4567, 76543, 23456789, 1111111111111111111, 11111111111111111111111
Offset: 1

Views

Author

Omar E. Pol, Nov 14 2009

Keywords

Comments

Prime numbers with 2 digits together with the primes whose digits are in arithmetic progression. The structure of digits represents a straight line.
Note that in the graphic representation the points are connected by imaginary line segments (see also A135643).
Note that all two-digit primes are straight-line primes but this sequence has no three-digit terms.
No further terms between 23456789 and 115507867=prime(6600000). - R. J. Mathar, Dec 04 2009
All terms after 23456789 are repunit primes (A004022) with number of digits: 19, 23, 317, 1031, 49081, 86453, 109297, 270343, ... (A004023). - Jens Kruse Andersen, Jul 21 2014

Examples

			The number 4567 is straight-line prime:
  . . . .
  . . . .
  . . . 7
  . . 6 .
  . 5 . .
  4 . . .
  . . . .
  . . . .
  . . . .
  . . . .
		

Crossrefs

Extensions

2 more terms from R. J. Mathar, Dec 04 2009
a(25)-a(26) from Jens Kruse Andersen, Jul 21 2014

A173071 Palindromic mountain primes.

Original entry on oeis.org

131, 151, 181, 191, 12421, 12721, 12821, 13831, 13931, 14741, 17971, 1235321, 1245421, 1257521, 1268621, 1278721, 1456541, 1469641, 1489841, 1579751, 1589851, 123484321, 123494321, 123575321, 136797631, 167898761, 12345854321
Offset: 1

Views

Author

Omar E. Pol, Feb 09 2010

Keywords

Comments

All terms have an odd number of digits. - Emeric Deutsch, Mar 09 2010

Examples

			a(6) = 12721; is a palindromic mountain prime.
. . . . .
. . . . .
. . 7 . .
. . . . .
. . . . .
. . . . .
. . . . .
. 2 . 2 .
1 . . . 1
		

Crossrefs

Programs

  • Maple
    a := proc (n) local rev, n1: rev := proc (n) local nn: nn := convert(n, base, 10): add(nn[j]*10^(nops(nn)-j), j = 1 .. nops(nn)) end proc: n1 := convert(n, base, 10): if n1[1]=1 and isprime(n) = true and rev(n) = n and n1[1] < n1[2] and n1[2] < n1[3] and n1[3] < n1[4] then n else end if end proc: seq(a(n), n = 1000000 .. 9999999); # this program works only for 7-digit numbers; easily adjustable for other (2k+1)-digit numbers # Emeric Deutsch, Mar 09 2010
  • Python
    from itertools import combinations
    from gmpy2 import is_prime
    A173071_list = []
    for l in range(1,10):
        for i in combinations('23456789',l):
            s = '1'+''.join(i)
            p = int(s+s[l-1::-1])
            if is_prime(p):
                A173071_list.append(p) # Chai Wah Wu, Nov 05 2015

Extensions

More terms from Emeric Deutsch, Mar 09 2010, corrected Mar 19 2010
a(22)-a(27) from Donovan Johnson, Jul 22 2010

A244369 Palindromic right-angled primes.

Original entry on oeis.org

101, 787, 34543, 7654567, 345676543, 34567876543
Offset: 1

Views

Author

Omar E. Pol, Jun 26 2014

Keywords

Comments

Intersection of A002113 and A167842.
Intersection of A002385 and A135602.
The last term of this sequence is also the last term of A134811.

Examples

			Illustration of a(6) = 34567876543, the last term of this sequence:
. . . . . . . . . . .
. . . . . 8 . . . . .
. . . . 7 . 7 . . . .
. . . 6 . . . 6 . . .
. . 5 . . . . . 5 . .
. 4 . . . . . . . 4 .
3 . . . . . . . . . 3
. . . . . . . . . . .
. . . . . . . . . . .
. . . . . . . . . . .
		

Crossrefs

Programs

  • Python
    from sympy import isprime
    A244369 = []
    for n in range(1,10):
        for m in range(n-1,-1,-1):
            l = ''.join([str(d) for d in range(n,m-1,-1)])
            p = int(l+l[-2::-1])
            if isprime(p):
                A244369.append(p)
        for m in range(n+1,10):
            l = ''.join([str(d) for d in range(n,m+1)])
            p = int(l+l[-2::-1])
            if isprime(p):
                A244369.append(p)
    A244369 = sorted(A244369) # Chai Wah Wu, Aug 15 2014

A182775 Giza nonprimes.

Original entry on oeis.org

1, 4, 6, 8, 9, 121, 232, 343, 454, 565, 676, 898, 12321, 23432, 45654, 56765, 67876, 78987, 1234321, 2345432, 3456543, 4567654, 5678765, 6789876, 123454321, 234565432, 456787654, 567898765, 12345654321, 23456765432, 45678987654
Offset: 1

Views

Author

Omar E. Pol, Dec 16 2010

Keywords

Comments

I propose the name Giza nonprimes.
The total number of terms is 37. The largest is 12345678987654321 which is also the largest mountain number A134941.

Examples

			a(6)=121 is in the sequence because 121 is a nonprime number A018252 and 121 is also a Giza number A134810.
The last six terms of this finite sequence are
a(32) = 1234567654321
a(33) = 2345678765432
a(34) = 3456789876543
a(35) = 123456787654321
a(36) = 234567898765432
a(37) = 12345678987654321
Illustration of a(37) as a Giza nonprime:
. . . . . . . . 9 . . . . . . . .
. . . . . . . 8 . 8 . . . . . . .
. . . . . . 7 . . . 7 . . . . . .
. . . . . 6 . . . . . 6 . . . . .
. . . . 5 . . . . . . . 5 . . . .
. . . 4 . . . . . . . . . 4 . . .
. . 3 . . . . . . . . . . . 3 . .
. 2 . . . . . . . . . . . . . 2 .
1 . . . . . . . . . . . . . . . 1
		

Crossrefs

Programs

  • Mathematica
    Select[Union[FromDigits/@Select[Flatten[Table[Table[Join[Range[i,i+n], Reverse[ Most[ Range[ i,i+n]]]],{n,0,9}],{i,9}],1],Max[#]<10&]], !PrimeQ[#]&] (* Harvey P. Dale, Aug 23 2011 *)

Formula

A018252 INTERSECT A134810.
Showing 1-8 of 8 results.