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A272041
Smallest integer that can be expressed as the sum of n primes in at least n distinct ways.
1
2, 10, 15, 18, 19, 22, 25, 27, 29, 32, 34, 36, 39, 42, 44, 46, 49, 51, 53, 55, 58, 60, 63, 65, 67, 69, 72, 74, 76, 78, 80, 83, 85, 87, 90, 92, 94, 96, 98, 100, 102, 105, 107, 109, 111, 113, 115, 117, 120, 122, 124, 126, 128, 131, 133, 135, 137, 139, 141, 143
OFFSET
1,1
COMMENTS
Initial terms found by exhaustive search in Excel.
LINKS
Lars Blomberg and Giovanni Resta, Table of n, a(n) for n = 1..5000 (first 99 terms from Lars Blomberg)
EXAMPLE
The sequence is defined here as starting at n=1 to avoid the term a(0). Even though there cannot be exactly zero ways to add zero primes, there is always at least one way to add 0 primes to get any n (i.e., the sum of itself for any nonprime or (1+..+1) for any prime), and zero would be the lowest such number.
Sum of 1 prime in 1 way: 2.
Sum of 2 primes in 2 ways: 3+7 = 5+5 = 10.
Sum of 3 primes in 3 ways: 3+5+7 = 5+5+5 = 2+2+11 = 15.
Sum of 4 primes in 4 ways: 2+2+3+11 = 2+2+7+7 = 3+3+5+7 = 3+5+5+5 = 18.
Sum of 60 primes in 61 ways, e.g.: 57*2 + 3 + 7 + 19 = 37*2 + 23*3 = 143. - Lars Blomberg, Jul 18 2017
MATHEMATICA
a[n_] := Block[{k = 1}, While[Length@ Quiet@ IntegerPartitions[k, {n}, Prime@ Range@ PrimePi@ k, n] < n, k++]; k]; Array[a, 50]
CROSSREFS
Sequence in context: A065989 A299378 A031222 * A212160 A134861 A063610
KEYWORD
nonn
AUTHOR
Matthew Ryan, Apr 21 2016
EXTENSIONS
a(36)-a(60) from Lars Blomberg, Jul 18 2017
STATUS
approved