Those Fascinating Numbers 307
27 412 679
the number of twin prime pairs 1010 (see the number 1 224).
27 644 437
the 13th Bell number (see the number 52).
28 119 418
the sixth even number n such that σI (n) = σI (n + 2) (see the number 54 178).
28 600 321 (= 312 · 29761)
the second 30-hyperperfect number (see the number 3 901).
29 149 139
the smallest number n for which the Moebius function µ takes on successively,
starting with n, the values 1,0,1,0,1,0,1,0,1,0,1,0,1,0,1,0 (see the number 3 647).
30 002 960
the 17th number n such that φ(n) + σ(n) = 3n (see the number 312).
30 042 907
the largest known number whose square is the sum of a cube and an eighth
power: here 30 042 9072 = 96 2223 + 438 (see the number 122).
30 402 457
the exponent of the 43rd Mersenne prime 230 402 457 1 (a 9 152 052 digit num-
ber) discovered by Curtis Cooper and Steven Boone on December 15, 2005,
using the programme developed by G. Woltman (see the number 1 398 269).
30 459 361 (= 55192)
the smallest powerful number n such that n +14 is also powerful: here n +14 =
33
·
55
·
192;
the sequence of numbers satisfying this property begins as follows:
30 459 361, 717 498 661, 1 090 122 275, 185 344 887 289,. . .
192.
192This sequence is infinite (see the number 214 369).
Previous Page Next Page