20123

Properties

Appears in sequences

• Number of nonnegative solutions to x^2 + y^2 + z^2 <= n^2.at n=33A000604
• Primes that remain prime through 3 iterations of function f(x) = 2x + 7.at n=19A023275
• Primes that remain prime through 4 iterations of function f(x) = 2x + 7.at n=5A023305
• Primes that remain prime through 5 iterations of function f(x) = 2x + 7.at n=1A023333
• Partition the sequence of natural numbers into groups so that each group product is just >=n! until the group contains only one number which is >= n!; a(n) = the number of such groups.at n=7A092980
• Duplicate of A092980.at n=7A094532
• Primes p such that q = 4p^2 + 1 and r = 4q^2 + 1 are also prime.at n=28A122424
• Primes congruent to 36 mod 53.at n=39A142566
• Primes congruent to 4 mod 59.at n=37A142731
• Primes congruent to 54 mod 61.at n=37A142852
• Append three digits, each increasing by one modulo 10 from the last digit of the nonnegative integers. 0 -> 123, 1 -> 1234 2 -> 2345, ... , 9 -> 9012, 10 -> 10123, etc.at n=20A167231
• Primes p such that 3*p+4, 5*p+6 and 7*p+8 are also prime.at n=22A173879
• Incorrect duplicate of A062343.at n=29A176254
• Fibonacci + Goldbach (dual sequence to A216275). a(1)=5, a(2)=7 and for n>=3, a(n) = g(a(n-1) + a(n-2)), where for m>=3, g(2*m) is the maximal prime p < 2*m such that 2*m - p is prime.at n=20A216835
• Primes in A065387 in the order of their appearance.at n=33A229264
• Primes p of the form penta(n)-3, where penta(n) is the n-th pentagonal number.at n=28A232537
• Conjecturally, the largest k such that prime(n)^2 is the largest squared prime divisor of binomial(2k,k).at n=29A239623
• a(n+1) is the smallest prime > a(n) such that the digits of a(n) are all (with multiplicity) contained in the digits of a(n+1), with a(1)=2.at n=8A242904
• Primes p such that p^3 - 1 has 8 divisors.at n=19A341659
• Prime numbers representing a date based on the proleptic Gregorian calendar in YY..YMMDD format.at n=36A352947