Sequences

Sort-then-add sequence: a(1) = 316, a(n+1) = a(n) + sort(a(n)).

Sorted number reached from starter n in Sort-then-add sequence, or -1 if never reaches sorted number.

Least number of Sort-then-add persistence n.

Sorted number reached from A033863(n) by Sort-then-add.

Start with n; if palindrome, stop; otherwise add to itself with digits reversed; a(n) gives palindrome at which it stops, or -1 if no palindrome is ever reached.

Least number of Reverse-then-add persistence n.

Palindrome reached from A033866(n) by Reverse-then-add.

Numbers n such that 7*n-11 is prime.

Weight distribution of [79,40,15] binary quadratic-residue (or QR) code.

Divisors = 1 (mod 4) of Descartes's 198585576189.

Divisors = 3 (mod 4) of Descartes's 198585576189.

Numbers k such that A033831(k) is prime.

Difference between first prime > 10^n (A003617) and 10^n.

Difference between the largest prime < 10^n (A003618) and 10^n.

Skipping from prime to prime by least powers of 2.

Expansion of 1/(2*x) * (1/(1-4*x)^(3/2)-1).

Triangular array read by rows associated with Schroeder numbers: T(1,k) = 1; T(n,k) = 0 if k < n; T(n,k) = T(n,k-1) + T(n-1,k-1) + T(n-1,k).

Triangular array associated with Schroeder numbers.

Deficiency of n, or 2n - (sum of divisors of n).

Abundance of n, or (sum of divisors of n) - 2n.

Abundancy of n-th abundant number: sigma(k) - 2k for k such that this is > 0.

Abundancy of the abundant or perfect numbers: m = sigma(k)-2k for n such that m >= 0.

Deficiency of the deficient or perfect numbers: m = 2n - sigma(n) for n such that m >= 0.

Deficiency of n-th deficient number: 2k - sigma(k) for k such that this is > 0.

a(n) = 3*n - sum of divisors of n.

Number of connected 4-regular simple graphs on n vertices with girth at least 4.

a(n) = Fibonacci(3*n + 1).

a(n) = Fibonacci(4*n).

a(n) = Fibonacci(4*n + 1).

a(n) = Fibonacci(4*n + 2).

a(n) = Fibonacci(4*n+3).

Orders of subgroups of M24.

Sort then Add, a(1)=3.

Sort then Add, a(1)=5.

Sort then Add, a(1)=7.

Sort then Add, a(1) =9.

Sort then Add, a(1)=13.

Sort then Add, a(1)=15.

Sort then Add, a(1)=17.

Sort then Add, a(1)=19.

Sort then Add, a(1)=21.

Sort then Add, a(1)=25.

Sort then Add, a(1)=27.

Sort then Add, a(1)=29.

Sort then Add, a(1)=31.

Sort then Add, a(1)=20.

Sort then Add, a(1)=32.

Least number of Sort-then-add persistence n.

Number of Sort then Add steps needed to reach a sorted number, or -1 if never reach sorted number.

Numbers k such that s(k) + s(k+1) + s(k+2) = t(k) + t(k+1) + t(k+2) where s(k) = sigma(k) - k, t(k) = |s(k) - k|.