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.

A111471 a(1) = 1; for n>1, a(n) = least k such that concatenation of n copies of k with all previous concatenations gives a prime.

Original entry on oeis.org

1, 9, 7, 3, 29, 19, 21, 121, 7, 211, 207, 11, 221, 347, 99, 123, 303, 189, 1131, 1179, 2069, 3437, 2211, 211, 3169, 1551, 3493, 7433, 6939, 1053, 1537, 9417, 4491, 1257, 19693, 9, 1653, 3329, 317, 8667, 799, 1053, 5617, 6049, 1721, 24871, 2751, 737, 3303, 29079
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Examples

			199, 199777, 1997773333, 19977733332929292929 are all primes.

Crossrefs

Cf. A111472.

Extensions

More terms from Donovan Johnson, Feb 26 2008

A111473 a(1) = 3, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

Original entry on oeis.org

3, 1, 1, 11, 113, 7, 23, 41, 37, 141, 733, 241, 3, 791, 781, 701, 239, 441, 2019, 189, 2071, 401, 851, 463, 4421, 497, 2267, 213, 1653, 1683, 1227, 667, 3261, 6673, 5799, 3579, 1907, 6483, 7813, 2443, 1923, 11439, 6657, 7861, 1847, 7521, 8277, 8459
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Examples

			3,311,311111,31111111111111 are all prime.
31111111111111 = one copy of 3, two copies of 1, three copies of 1, four copies of 11.

Crossrefs

Cf. A111471, A111472, A111474.

Programs

  • PARI
    { x=3; for(n=2,50, k=0; until(ispseudoprime(y), k++; y=eval(concat(Str(x),concat(vector(n,i,Str(k))))); ); print1(k,", "); x=y; ) } \\ Max Alekseyev, May 18 2009

Extensions

More terms from Max Alekseyev, May 18 2009

A111475 a(1) = 7, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

Original entry on oeis.org

7, 3, 1, 1, 1, 1, 129, 123, 97, 559, 781, 459, 253, 183, 413, 417, 657, 77, 437, 1439, 667, 1281, 3379, 979, 2763, 1953, 103, 10083, 5103, 291, 1311, 2199, 1159, 501, 5931, 483, 6171, 16301, 1781, 1229, 9519, 607, 5113, 2641, 1441, 8511, 9023, 363, 4001, 15261
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Examples

			7,733,733111,... are all prime.
733111 = one copy of 7, two copies of 3, three copies of 1.

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111476.

Extensions

Extended by Max Alekseyev, May 19 2009

A111478 Primes pertaining to A111477.

Original entry on oeis.org

11, 111919, 111919191919, 11191919191937373737, 111919191919373737372121212121, 111919191919373737372121212121717171717171, 111919191919373737372121212121717171717171101101101101101101101
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Examples

			111919191919 = one copy of 11, two copies of 19, three copies of 19.

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111475, A111477.

Extensions

More terms from Tracy Poff (tracy.poff(AT)gmail.com), Dec 31 2005

A111477 a(1) = 11, a(n) = least k such that concatenation of n copies of k with all previous concatenation gives a prime.

Original entry on oeis.org

11, 19, 19, 37, 21, 71, 101, 39, 61, 87, 227, 63, 437, 153, 1363, 117, 363, 861, 609, 249, 23, 1077, 3123, 771, 3717, 633, 279, 1119, 927, 107, 3843, 4313, 1729, 627, 12541, 2403, 4083, 1239, 2227, 6441, 3819, 3983, 5631, 2303, 2971, 19217, 3633, 5109, 14413, 913
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Examples

			11,111919,111919191919,... are all prime.
111919191919 = one copy of 11, two copies of 19, three copies of 19.

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111475, A111478.

Extensions

a(4)-a(8) from Stefan Steinerberger, Nov 17 2005
Extended by Max Alekseyev, May 20 2009

A111476 Primes pertaining to A111475.

Original entry on oeis.org

7, 733, 733111, 7331111111, 733111111111111, 733111111111111111111, 733111111111111111111129129129129129129129, 733111111111111111111129129129129129129129123123123123123123123123
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111475.

Extensions

Extended by Max Alekseyev, May 19 2009

A111479 a(n) = least positive number such that (2 Concat Concat_{k=1}^n Repeat(A045572(n), a(n))) is a prime. A045572 = odd numbers not divisible by 5.

Original entry on oeis.org

2, 1, 4, 11, 3, 617, 96, 1213, 1965
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Comments

Concat is the operator that concatenates two numbers as decimal strings and Repeat returns the number obtained by concatenating the first argument to itself the second argument number of times.

Examples

			21 is not a prime, but 211 is, so a(1)=2.
211,2113,21137777 are all primes. 21137777 is a prime obtained as 2 followed by two 1's, one 3 and four 7's, so a(2) = 4.

Crossrefs

Cf. A111471, A111472, A111473, A111475, A111477, A111478, A111480.

Extensions

Edited by Franklin T. Adams-Watters, Aug 29 2006.
Corrected and extended by Max Alekseyev, May 21 2009

A111480 Primes pertaining to A111479.

Original entry on oeis.org

211, 2113, 21137777, 2113777799999999999, 2113777799999999999111111
Offset: 1

Views

Author

Amarnath Murthy, Aug 05 2005

Keywords

Comments

The next term is 21137777999999999991111111313...13 where the number of trailing 13's is 617. It has 1259 decimal digits.

Crossrefs

Cf. A111471, A111472, A111473, A111474, A111475, A111477, A111478, A111479.

Extensions

Corrected by Max Alekseyev, May 21 2009
Showing 1-8 of 8 results.

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