30555

Appears in sequences

• Numbers m such that phi(m) = tau(m)^3.at n=18A068559
• Odd numbers k such that abs(sigma(k)-2k) <= sqrt(k). Abundance-radius = abs(sigma(k)-2k) does not exceed square root of k and k is odd.at n=14A087415
• Odd admirable numbers: such that sigma(n) = 2n + 2d for some d | n.at n=9A109729
• Triangle T(n, m) = T(n-1, m-1) + (4m-3)*T(n-1, m) read by rows 1<=m<=n.at n=32A111578
• Increasing gaps in the even sieve (A056533) by lower term.at n=21A119503
• a(n) = 25*n^2 - 2*n.at n=34A154376
• Half the difference between the larger and smaller term of the n-th amicable pair.at n=37A162884
• (2n^7 + 4n^6 - n^5 - 4n^4 - n^3) / 24.at n=6A245940
• Half the difference between the larger and smaller terms of the n-th amicable pair (x,y) given in A259933.at n=37A275470
• Admirable numbers such that the subtracted divisor is a Fibonacci number.at n=20A282754
• Irregular triangle read by rows where row n lists all odd primitive abundant numbers with n prime factors, counted with multiplicity.at n=37A287646
• Numbers k such that 30*k - 1, 30*k + 1, 30*k^2 - 1 and 30*k^2 + 1 are all prime.at n=40A359184
• Square array T(n,k), n >= 1, k >= 1, read by antidiagonals, where T(n,k) = Sum_{1 <= x_1, x_2, ..., x_k <= n} gcd(x_1, x_2, ..., x_k, n)^k.at n=50A372938
• Square array read by antidiagonals upwards: T(i,j) is the smallest number m such that the symmetric representation of sigma, SRS(m), has maximum width 3, consists of i parts and has 2*j occurrences of maximum width 3 in its width pattern (row m of A341969).at n=17A377667
• Odd numbers k such that gcd(A276086(sigma(k)-k), A276086(k)) is equal to A276086(k), where A276086 is the primorial base exp-function, and sigma is the sum of divisors function.at n=20A388267
• Numbers k whose abundance is 42: sigma(k) - 2*k = 42.at n=1A391615