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 1-3 of 3 results.

A072686 Prime numbers whose (British) English names have a prime number of letters.

Original entry on oeis.org

2, 3, 7, 23, 37, 79, 83, 97, 109, 139, 157, 163, 167, 199, 211, 229, 239, 257, 263, 271, 313, 401, 421, 431, 449, 491, 503, 521, 569, 643, 647, 653, 709, 719, 751, 761, 809, 907, 991, 1021, 1031, 1049, 1069, 1091, 1103, 1301, 1303, 1307, 1327, 1409, 1511
Offset: 0

Views

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 02 2002

Keywords

Comments

See A231075 for the American English version. The sequences coincide up to a(8)=97 but are then completely different, due to the additional "and" (e.g. in "one hundred and nine") in the British style. - M. F. Hasler, Nov 03 2013

Examples

			e.g. 2003 -> "TWOTHOUSANDANDTHREE" -> 19 letters and 19 is prime. Note that the "and" naming convention is used; e.g. "ONE HUNDRED AND ONE", "ONE THOUSAND NINE HUNDRED AND SEVENTY THREE".

Links

Crossrefs

Prime elements of A072685.

A163648 Primes p with a prime number of syllables in their name in American English.

Original entry on oeis.org

7, 11, 13, 17, 19, 23, 29, 31, 41, 43, 53, 59, 61, 83, 89, 107, 113, 127, 137, 157, 167, 173, 179, 197, 227, 257, 271, 307, 313, 337, 347, 367, 373, 379, 397, 419, 457, 467, 479, 487, 547, 557, 571, 587, 607, 613, 619, 647, 673, 701, 709, 733, 739, 743, 751
Offset: 1

Views

Author

Jonathan Vos Post, Aug 02 2009

Keywords

Comments

The word "and" is excluded, 101 is "one hundred one" rather than "one hundred and one."
See A231073 and A231075 for the analogs counting words resp. letters. - M. F. Hasler, Nov 03 2013

Examples

			a(1) = 7, which has a prime number, 2, of syllables sev-en. a(2) = 11, which has a prime number, 3, of syllables e-lev-en.

Links

Crossrefs

Cf. A000040, A075774, A164043.

Programs

Formula

{p in A000040 such that A075774(p) is in A000040}.

Extensions

Extended and edited by Charles R Greathouse IV, Nov 02 2009
Values double-checked by M. F. Hasler, Nov 03 2013

A230956 Semiprimes k with a semiprime number of syllables in their name in American English.

Original entry on oeis.org

57, 74, 87, 106, 111, 121, 122, 123, 129, 133, 134, 141, 142, 143, 145, 146, 155, 158, 159, 161, 166, 169, 183, 185, 194, 201, 202, 203, 205, 206, 209, 217, 221, 226, 235, 249, 253, 254, 259, 262, 265, 289, 291, 295, 298, 299, 301, 302, 303, 305, 309
Offset: 1

Views

Author

Jonathan Vos Post, Nov 04 2013

Keywords

Comments

This is to A163648 as semiprimes A001358 are to primes A000040.
The word "and" is excluded, 101 is "one hundred one" rather than "one hundred and one."
Number of syllables in n in American English is A075774.
See A231073 and A231075 for prime analogs counting words respectively letters.

Examples

			87 is in the sequence because 87 = 3 * 29 is semiprime, "eighty-seven" has 4 syllables, and 4 = 2^2 is also semiprime.
106 is in the sequence because 106 = 2 * 53 is semiprime and "one hundred six" has semiprime 4 syllables.
111 is in the sequence because 111 = 3 * 37 is semiprime and "one hundred eleven" has semiprime 6 = 2*3 syllables.

Links

Crossrefs

Cf. A001358, A075774, A163648, A231073, A231075.

Programs

  • Python
    # uses function in A075774
from sympy import factorint
def issemiprime(n): return sum(factorint(n).values()) == 2
def ok(n): return issemiprime(A075774(n)) and issemiprime(n)
print([k for k in range(310) if ok(k)]) # Michael S. Branicky, May 27 2024

Formula

{k: k is in A001358 and A075774(k) is in A001358}.

Extensions

Corrected and extended by Charles R Greathouse IV, Jan 23 2014
Showing 1-3 of 3 results.

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

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