A254859 Numbers that are both a sum and a product of two or more consecutive primes.
15, 30, 77, 143, 210, 221, 323, 1001, 2310, 4199, 5767, 7429, 9797, 10403, 11021, 12317, 20711, 22499, 23707, 25591, 28891, 30030, 33263, 34571, 36863, 38021, 46189, 47053, 75067, 77837, 79523, 82861, 82919, 89951, 95477, 99221, 104927, 111547, 116939, 136891, 141367, 145157, 146969, 154433
Offset: 1
Examples
15 is a term because 15 = 3 + 5 + 7 = 3*5. 30 is a term because 30 = 13 + 17 = 2*3*5. 77 is a term because 77 = 2 + 3 + 5 + 7 + 11 + 13 + 17 + 19 = 7*11.
Links
- Michael S. Branicky, Table of n, a(n) for n = 1..4381 (terms 1..644 from Amiram Eldar)
- Michael S. Branicky, Python program
Programs
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Mathematica
np = NextPrime; pro[n_] := Block[{e, f}, {f, e} = Transpose@ FactorInteger@ n; Length@ f > 1 && Union@ e == {1} && np@ Most@ f == Rest@ f]; seq[lim_] := Union[Reap[Block[{p = 2, q, s}, While[2 p < lim, q = np@p; s = p+q; While[s <= lim, If[pro@s, Sow@s]; q = np@q; s += q]; p = np@p]]][[2, 1]]]; seq[10^5] (* Giovanni Resta, May 05 2016 *)
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Python
# see link