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.

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A297893 Numbers that divide exactly three Euclid numbers.

Original entry on oeis.org

3041, 24917, 144671, 224251, 278191, 301927, 726071, 729173, 772691, 1612007, 1822021, 1954343, 2001409, 2157209, 2451919, 2465917, 2522357, 2668231, 3684011, 3779527, 3965447, 4488299, 4683271, 4869083, 5244427, 5650219, 6002519, 6324191, 6499721, 7252669
Offset: 1

Views

Author

Jon E. Schoenfield, Jan 07 2018

Keywords

Comments

A113165 lists numbers those numbers (> 1) that divide at least one Euclid number; A297891 lists those that divide exactly two Euclid numbers.
Is this sequence infinite?
Does this sequence contain any nonprimes?
Are there any numbers > 1 that divide more than three Euclid numbers?
The first numbers that divide 4 and 5 Euclid numbers are 15415223 and 2464853, respectively. - Giovanni Resta, Jun 26 2018

Examples

			a(1) = 3041 because 3041 is the smallest number that divides exactly three Euclid numbers: 1 + A002110(206), 1 + A002110(263), and 1 + A002110(409); these numbers have 532, 712, and 1201 digits, respectively.

Links

Crossrefs

Cf. A002110 (primorials), A006862 (Euclid numbers), A113165 (numbers > 1 that divide Euclid numbers), A297891 (numbers > 1 that divide exactly two Euclid numbers).

Extensions

a(14)-a(30) from Giovanni Resta, Jun 26 2018

A297894 Composite numbers that divide at least one Euclid number.

Original entry on oeis.org

1843, 5263, 10147, 12629, 24047, 26869, 30031, 136109, 189001, 356189, 510511, 648077, 709493, 960359, 1293109, 1459817, 1513817, 1755431, 2263607, 2290129, 2578327, 2825041, 3173707, 3415703, 3440471, 4629071, 5007641, 5497781, 5698237, 6021971, 8614843
Offset: 1

Views

Author

Jon E. Schoenfield, Jan 07 2018

Keywords

Comments

The k-th Euclid number, A006862(k), is 1 plus the product of the first k primes, i.e., 1 + A002110(k). A113165 lists the numbers (> 1) that divide at least one Euclid number. It appears that the vast majority of terms in A113165 are prime; this sequence lists the composite numbers in A113165.
No composite less than 10^8 divides more than one Euclid number.

Examples

			a(1) = 1843 because 1843 = 19*97 is the smallest composite number that divides a Euclid number: 1843 divides 1 + A002110(7) = 1 + 2*3*5*7*11*13*17 = 510511 = 19*97*277. (Thus, 5263 (= 19*277), 26869 (= 97*277), and 19*97*277 = 510511 itself are also composites that divide a Euclid number; 5263 = a(2), 26869 = a(6), and 510511 = a(11).)

Crossrefs

Cf. A002110 (primorials), A006862 (Euclid numbers), A113165 (numbers > 1 that divide Euclid numbers), A297891 (numbers > 1 that divide exactly two Euclid numbers).
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Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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